Currently the methods of `AttributeMethods::PrimaryKey` are overwritten
by `define_attribute_methods`. It will be broken if a table that
customized primary key has non primary key id column.
It should not be overwritten if a table has any primary key.

Fixes #29350.

- Rename test cases from  `unknown` to `unrecognized` since unknown OID
is one of possible unrecognized types by Rails

- Use "select 'pg_catalog.pg_class'::regclass" whose OID is 2205, which
will not be converted to recognized type in PostgreSQL 10.

activerecord_unittest=# select oid, typname from pg_type where oid in (2205, 2277);
 oid  | typname
------+----------
 2205 | regclass
 2277 | anyarray
(2 rows)

Addresses #28868

These `assert_nothing_raised` are covered by following assertions.

`ReservedWordTest` expects that any identifiers are quoted properly.
It should be tested for all adapters.

In `test_schema_dump_includes_limit_constraint_for_integer_columns`,
unified `assert_match` and `assert_no_match` to simple regex.

This regression is caused by d1249c1a.

If STI model is defined `default_scope`, `base_rel` is not respected.
I fixed to merge `base_rel` in that case.

If casted value is nil, generated SQL should be `IS NULL`. But currently
it is generated as `= NULL`. To prevent this behavior, avoid making bind
param if casted value is nil.

Fixes #28945.

The assert_same above obviously guarantees this will pass, but this
seems less likely to be deleted just because the implementation changed.

`quote_default_expression` can be passed nil value when `null: true` and
`default: nil`. This addressed in that case.

Fixes #29222.

Structured type values sometimes caused representation problems (keys
sort order, spaces, etc). A raw value from the database should be
deserialized (normalized) to prevent the problems.

Formerly, `rename_table` only renamed primary key index name if the
column's data type was sequential (serial, etc in PostgreSQL). The
problem with that is tables whose primary keys had other data types
(e.g. UUID) maintained the old primary key name. So for example,
if the `cats` table has a UUID primary key, and the table is renamed to
`felines`, the primary key index will still be called `cats_pkey`
instead of `felines_pkey`. This PR corrects it.

Deprecate passing arguments and block at the same time to `count` and `sum` in `ActiveRecord::Calculations`

`select`, `count`, and `sum` in `Relation` are also `Enumerable` method
that can be passed block. `select` with block already doesn't take
arguments since 4fc3366d. This is follow up of that.

Some third party modules expects that association returns same proxy
object each time (e.g. for stubbing collection methods:
https://github.com/rspec/rspec-rails/issues/1817).
So I decided that cache the proxy object and reset scope in the proxy
object each time.

Related context: https://github.com/rails/rails/commit/c86a32d7451c5d901620ac58630460915292f88b#commitcomment-2784312

This fixes the following issues.

* `association_scope` doesn't include `default_scope`. Should use `scope` instead.
* We can't use `method_missing` for customizing existing method.
* We can't use `relation_delegate_class` for sharing extensions. Should extend per association.

a user input for a decimal column were ignored by numerically validations

[Vikrant Chaudhary, David Abdemoulaie, Matthew Draper]

Follow up of #27399.

Follow up of #25702.

".. with __dir__ we can restore order in the Universe." - by @fxn

Related to 5b8738c2

This was added at #22125 but `left_joins_values` is never used.

Both `mysql2/json_test.rb` and `postgresql/json_test.rb` have same test
cases.