Follow up to #38990.

Default engine `ENGINE=InnoDB` is no longer dumped to make schema more agnostic

Copy options before delegating in with_options

Otherwise we cannot handle the same name options for both column and
table (e.g. `:comment`, `:charset`, `:collation`).

5 years ago, I made dumping full table options at #17569, especially to
dump `ENGINE=InnoDB ROW_FORMAT=DYNAMIC` to use utf8mb4 with large key
prefix.

In that time, omitting the default engine `ENGINE=InnoDB` was not useful
since `ROW_FORMAT=DYNAMIC` always remains as long as using utf8mb4 with
large key prefix.

But now, MySQL 5.7.9 has finally changed the default row format to
DYNAMIC, utf8mb4 with large key prefix can be used without dumping the
default engine and the row format explicitly.

So now is a good time to make the default engine is omitted.

Before:

```ruby
create_table "accounts", options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci", force: :cascade do |t|
end
```

After:

```ruby
create_table "accounts", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
end
```

To entirely omit `:options` option to make schema agnostic, I've added
`:charset` and `:collation` table options to exclude `CHARSET` and
`COLLATE` from `:options`.

Fixes #26209.
Closes #29472.

See also #33608, #33853, and #34742.

cd31e113 switched to passing options as
keyword arguments, which always creates a new hash.

9e4ff29f removed a now-unnecessary call
to `dup`, since the options could no longer be accidentally mutated.

a55620f3 switched back to passing
options as a positional argument for Ruby < 2.7, but didn't restore the
call to `dup`, which meant that the same options hash was now passed
with every method call and mutations leaked from one call to another.

Co-authored-by: NAnton Topchii <player1@infinitevoid.net>

`joins_values` is already `compact_blank!`ed, so `blank?` check is
entirely redundant.

Deprecate aggregations with group by duplicated fields

We've learned that `merge` causes duplicated multiple values easily, so
if we missed to deduplicate the values, it will cause weird behavior
like #38052, #39171.

I've investigated the deduplication for the values, at least that had
existed since Rails 3.0.

https://github.com/rails/rails/commit/bed9179aa1496f6d28891cf515af0d7e515ebbab

Aggregations with group by multiple fields was introduced at Rails 3.1,
but we missed the deduplication for the aggregation result, unlike the
generated SQL.

https://github.com/rails/rails/commit/a5cdf0b9eb860c4370ae5fde231e1b61f71b6b65

While the investigation, I've found that `annotate` is also missed the
deduplication.

I don't suppose this weird behavior is intended for both.

So I'd like to deprecate the duplicated behavior in Rails 6.1, and will
be deduplicated all multiple values in Rails 6.2.

To migrate to Rails 6.2's behavior, use `uniq!(:group)` to deduplicate
group fields.

```ruby
accounts = Account.group(:firm_id)

# duplicated group fields, deprecated.
accounts.merge(accounts.where.not(credit_limit: nil)).sum(:credit_limit)
# => {
#   [1, 1] => 50,
#   [2, 2] => 60
# }

# use `uniq!(:group)` to deduplicate group fields.
accounts.merge(accounts.where.not(credit_limit: nil)).uniq!(:group).sum(:credit_limit)
# => {
#   1 => 50,
#   2 => 60
# }
```

- Language changes around the deliver_later note.
- Leave out "now", this is not a new feature anymore
- Drops lots repetitive "just" and "simple"

Deduplicate same clauses in `merge`

Fix through association with source/through scope which has joins

Related to #39328, #39358.

For now, `merge` cannot override non-equality clauses, so non-equality
clauses will easily be duplicated by `merge`.

This deduplicates redundant same clauses in `merge`.

Test Attached::Many in Attached::Many test

This exact test exists in `one_test.rb`.  It was probably overlooked
after being copied and pasted.

Reduce allocations in action_view cache expiry

Allow Erubi bufvar to be configured

This reverts 8538dfdc, which broke the
activemodel-serializers-xml gem.

We can still get most of the benefit by applying the optimisation from
7b391977 to empty hashes as well as nil.
This has the additional benefit of retaining the optimisation when the
user passes an empty options hash.

This allows `render_in` components that compile their own templates to
use their view context's current output buffer while a
`with_output_buffer` block is being evaluated.

Partially addresses #39377.

If source/through scope references other tables in where/order, we
should explicitly maintain joins in the scope, otherwise association
queries will fail with referenced unknown column.

Fixes #33525.

They may be cached for existing apps upgrading to 6.1. Follows up on #34477.

Fix through association to respect source scope for `includes`/`preload`

Decoding JSON dates should respect newlines

This fixes tests for missing backtraces

Errors *should* output their stack. Somehow these tests were passing
before. This clarifies all states (skip/fail/error) and works against
@tenderlove's patch.

`reflection.scope` is not aware of all source scopes if the association
is through association.

It should use `reflection.join_scopes` for that.

Fixes #39376.

Updates to nokogiri 1.10.9

Add `ActionDispatch::ActionableExceptions` to default middleware docs

Before #39304 was merged, backtraces would look like this:

```
$ be ruby -I lib:test test/controller/request_forgery_protection_test.rb -n test_ignores_trailing_slash_during_generation
Run options: -n test_ignores_trailing_slash_during_generation --seed 22205

E

Error:
PerFormTokensControllerTest#test_ignores_trailing_slash_during_generation:
NoMethodError: undefined method `have_cookie_jar?' for #<Object:0x00007f9ce19b9620>
    /Users/aaron/git/rails/actionpack/lib/action_controller/test_case.rb:522:in `ensure in process'
    /Users/aaron/git/rails/actionpack/lib/action_controller/test_case.rb:542:in `process'
    /Users/aaron/git/rails/actionpack/lib/action_controller/test_case.rb:395:in `get'
    test/controller/request_forgery_protection_test.rb:1005:in `test_ignores_trailing_slash_during_generation'

rails test test/controller/request_forgery_protection_test.rb:1004

Finished in 0.213230s, 4.6898 runs/s, 0.0000 assertions/s.
1 runs, 0 assertions, 0 failures, 1 errors, 0 skips
```

After #39304 was merged they look like this:

```
$ be ruby -I lib:test test/controller/request_forgery_protection_test.rb -n test_ignores_trailing_slash_during_generation
Run options: -n test_ignores_trailing_slash_during_generation --seed 62892

E

Error:
PerFormTokensControllerTest#test_ignores_trailing_slash_during_generation:
NoMethodError: undefined method `have_cookie_jar?' for #<Object:0x00007fa6d60193c8>

rails test test/controller/request_forgery_protection_test.rb:1004

Finished in 0.211953s, 4.7180 runs/s, 0.0000 assertions/s.
1 runs, 0 assertions, 0 failures, 1 errors, 0 skips
```

This patch reverts the part of #39304 that removes the backtrace.

Fixes #39088.

Resolve conflict between counter cache and optimistic locking

Satisfy Rubocop