Every database executes different type of sql statement to get metadata then `ActiveRecord::TestCase` ignores these database specific sql statements to make `assert_queries` or `assert_no_queries` work consistently.

Connection adapter already labels these statement by setting "SCHEMA" argument, this pull request makes use of "SCHEMA" argument to ignore metadata queries.

Here are the details of these changes:

* PostgresqlConnectionTest

Each of PostgresqlConnectionTest modified just executes corresponding methods

https://github.com/rails/rails/blob/fef174f5c524edacbcad846d68400e7fe114a15a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb#L182-L195

```ruby
        # Returns the current database encoding format.
        def encoding
          query_value("SELECT pg_encoding_to_char(encoding) FROM pg_database WHERE datname = current_database()", "SCHEMA")
        end

        # Returns the current database collation.
        def collation
          query_value("SELECT datcollate FROM pg_database WHERE datname = current_database()", "SCHEMA")
        end

        # Returns the current database ctype.
        def ctype
          query_value("SELECT datctype FROM pg_database WHERE datname = current_database()", "SCHEMA")
        end
```

* BulkAlterTableMigrationsTest

mysql2 adapter executes `SHOW KEYS FROM ...` to see if there is an index already created as below. I think the main concerns of these tests are how each database adapter creates or drops indexes then ignoring  `SHOW KEYS FROM` statement makes sense.

https://github.com/rails/rails/blob/fef174f5c524edacbcad846d68400e7fe114a15a/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb#L11

```ruby
          execute_and_free("SHOW KEYS FROM #{quote_table_name(table_name)}", "SCHEMA") do |result|
```

* Temporary change not included in this commit to show which statements executed

```diff
$ git diff
diff --git a/activerecord/test/cases/migration_test.rb b/activerecord/test/cases/migration_test.rb
index 8e8ed494d9..df05f9bd16 100644
--- a/activerecord/test/cases/migration_test.rb
+++ b/activerecord/test/cases/migration_test.rb
@@ -854,7 +854,7 @@ def test_adding_indexes

       classname = ActiveRecord::Base.connection.class.name[/[^:]*$/]
       expected_query_count = {
-        "Mysql2Adapter"     => 3, # Adding an index fires a query every time to check if an index already exists or not
+        "Mysql2Adapter"     => 1, # Adding an index fires a query every time to check if an index already exists or not
         "PostgreSQLAdapter" => 2,
       }.fetch(classname) {
         raise "need an expected query count for #{classname}"
@@ -886,7 +886,7 @@ def test_removing_index

       classname = ActiveRecord::Base.connection.class.name[/[^:]*$/]
       expected_query_count = {
-        "Mysql2Adapter"     => 3, # Adding an index fires a query every time to check if an index already exists or not
+        "Mysql2Adapter"     => 1, # Adding an index fires a query every time to check if an index already exists or not
         "PostgreSQLAdapter" => 2,
       }.fetch(classname) {
         raise "need an expected query count for #{classname}"
$
```

* Executed these modified tests

```ruby
$ ARCONN=mysql2 bin/test test/cases/migration_test.rb -n /index/
Using mysql2
Run options: -n /index/ --seed 8462

F

Failure:
BulkAlterTableMigrationsTest#test_adding_indexes [/home/yahonda/git/rails/activerecord/test/cases/migration_test.rb:863]:
3 instead of 1 queries were executed.
Queries:
SHOW KEYS FROM `delete_me`
SHOW KEYS FROM `delete_me`
ALTER TABLE `delete_me` ADD UNIQUE INDEX `awesome_username_index`  (`username`), ADD  INDEX `index_delete_me_on_name_and_age`  (`name`, `age`).
Expected: 1
  Actual: 3

bin/test test/cases/migration_test.rb:848

F

Failure:
BulkAlterTableMigrationsTest#test_removing_index [/home/yahonda/git/rails/activerecord/test/cases/migration_test.rb:895]:
3 instead of 1 queries were executed.
Queries:
SHOW KEYS FROM `delete_me`
SHOW KEYS FROM `delete_me`
ALTER TABLE `delete_me` DROP INDEX `index_delete_me_on_name`, ADD UNIQUE INDEX `new_name_index`  (`name`).
Expected: 1
  Actual: 3

bin/test test/cases/migration_test.rb:879

..

Finished in 0.379245s, 10.5473 runs/s, 7.9105 assertions/s.
4 runs, 3 assertions, 2 failures, 0 errors, 0 skips
$
```

* ActiveRecord::ConnectionAdapters::Savepoints

Left `self.ignored_sql` to ignore savepoint related statements because these SQL statements are not related "SCHEMA"

```
self.ignored_sql = [/^SAVEPOINT/, /^ROLLBACK TO SAVEPOINT/, /^RELEASE SAVEPOINT/]
```

https://github.com/rails/rails/blob/fef174f5c524edacbcad846d68400e7fe114a15a/activerecord/lib/active_record/connection_adapters/abstract/savepoints.rb#L10-L20

```ruby
      def create_savepoint(name = current_savepoint_name)
        execute("SAVEPOINT #{name}")
      end

      def exec_rollback_to_savepoint(name = current_savepoint_name)
        execute("ROLLBACK TO SAVEPOINT #{name}")
      end

      def release_savepoint(name = current_savepoint_name)
        execute("RELEASE SAVEPOINT #{name}")
      end
```

e.g. via test-unit-rails' `run_setup`

any? should be delegated to the errors list

Revert changes to monotonic times

Otherwise we get deprecation warnings in the generated scaffold template files

The change to monotonic times causes failures for applications
where the subscribed block is expecting Time objects as described
in this issue: https://github.com/rails/rails/issues/36145

The original PR (https://github.com/rails/rails/pull/35984) was
concerned with errors on the cpu_time. Test was edited to reflect
changes to initializer using 0 values instead of nil

[Guides] Remove dynamic_form gem reference in guides

[ci skip]

This gem has not been updated since April 2014 and 2 of the 4 methods it introduces have been broken since Rails 4

Should take the record's state of first action in the transaction

If the same id's records are saved and/or destroyed in the transaction,
commit callbackes will only run for the first enrolled record.

https://github.com/rails/rails/blob/a023e2180093ebc517a642aaf21f3c7241c67657/activerecord/lib/active_record/connection_adapters/abstract/transaction.rb#L115-L119

The regression #36132 is caused due to #35920 changed the enrollment
order that the first action's record will be enrolled to last in the
transaction.

We could not change the the enrollment order as long as someone depends
on the enrollment order.

Fixes #36132.

Action Mailer release notes [ci skip]

[ci skip] Add 6.0 Release Notes for Action View

Fix incorrect url in guide [ci skip]

The example functional test lists the 'create' route as article_url rather than articles_url

I've added release notes based off of the CHANGELOG for Action View.

Improve error message of ActiveSupport delegate

ActiveSupport `delegate` has `to` option, but it's not a option hash
anymore and now it's a keyword argument.
When `to` argument is not given, it raises an ArgumentError but
the message suggests supplying "options hash", which is now wrong.
Now it's fixed to provide correct suggestion to supply a keyword
argument.

[ci skip] Update the guide's model generator output.

The model generator code sample used in the command line guides
was displaying an outdated output for the generator's usage.
This change updates the sample to mirror what's currently output
when running `$rails generate model`.

Fix merging left_joins to maintain its own `join_type` context

This fixes a regression for #35864.

Usually, stashed joins (mainly eager loading) are performed as LEFT
JOINs.
But the case of merging joins/left_joins of different class, that
(stashed) joins are performed as the same `join_type` as the parent
context for now.
Since #35864, both (joins/left_joins) stashed joins might be contained
in `joins_values`, so each stashed joins should maintain its own
`join_type` context.

Fixes #36103.

* Fallback to spawn instead of fork in jruby

This commit: b342db68 introduced a `fork` fork when running the railties
tests since this is not supported in jruby we fallback to using spawn.
Fixes: https://github.com/rails/rails/issues/35900

* Add test asserting truncate returns unfrozen string

* Ensure strings returned from truncate are not frozen

This fixes an issue where strings too short to be truncated were
returned unfrozen, where as long-enough strings were returned
frozen. Now retuned strings will not be frozen whether or not
the string returned was shortened.

* Update changelog w/ new truncate behavior description

[Jordan Thomas + Rafael Mendonça França]

Add 6.0 Release Notes for Action Pack

I've gone through the CHANGELOG for Action Pack, pulled out anything
that was backported, rephrased some of the descriptions and found their
PR's/commits as links.

See 19770d6c.

Bump bootsnap to a version with disables iseq_cache for Ruby 2.5

- Refs https://github.com/Shopify/bootsnap/pull/257

Fixes grammar in comments on tag_name and tag_id

Bump gem version to 6.0.0.rc1.

Fix outdated yarn.lock