Refactor handling of :action default in routing

Example:

    create_table :users do |t|
      t.string :name
      t.index 'lower(name) varchar_pattern_ops'
    end

Fixes #19090.
Fixes #21765.
Fixes #21819.
Fixes #24359.
Signed-off-by: NJeremy Daer <jeremydaer@gmail.com>

There is no need to fetch all table indexes in remove_index if name is specified. If name is wrong, then StatementInvalid will be raised.
Signed-off-by: NJeremy Daer <jeremydaer@gmail.com>

- Rename max to statement_limit
- Remove magic number 1000 from everywhere
- Defined StatementPool::DEFAULT_STATEMENT_LIMIT and started using it everywhere
Signed-off-by: NJeremy Daer <jeremydaer@gmail.com>

This alternative flows better.

[Richard Schneeman & Xavier Noria]

`railtie` is already a string!

Adapters override `#supports_savepoints?` to return `true` if they
support transaction savepoints. Defaults to `false`.

Awaken waiting threads even if the current thread (the previously
exclusive thread) hadn't taken a share lock.

This only happens in code that wasn't run within an executor, since that
always take an outermost share lock.

:nodoc: internal StatementPool class

 [ci skip]

Add #23461 to release notes

[ci skip]

Fix broken build, channel files are also included in `bin/rails stats` now

- Followup of https://github.com/rails/rails/pull/24709.

add channels files in `stats` task

Add prepared statements support for `Mysql2Adapter`

Deprecate `request_via_redirect` method.

Move `select_rows` implementation to super class

Add `:nodoc:` to `insert_versions_sql` [ci skip]

Remove in the doc about MySQL versions below 5 [ci skip]

Move `require 'ipaddr'` in `postgresql/oid/cidr.rb`

`IPAddr` is used in `OID::Cidr`.

Follow up to #23458.
Active Record supports MySQL >= 5.0 now.

Follow up to #24685. `insert_versions_sql` is not public API.

- Followup of https://github.com/rails/rails/issues/18693.
- I think we missed deprecating `request_via_redirect` in that pull
  request.
- Originally requested by DHH here
  https://github.com/rails/rails/issues/18333.

Fix typo in ActiveJob #retry_job doc

Followup of #15771

Make sure we handle explicitly passed nil's to lock_version as well.
An explicitly passed nil value is now converted to 0 on LockingType,
so that we don't end up with ActiveRecord::StaleObjectError in update record
optimistic locking

Fixes #24695

Follow up of https://github.com/rails/rails/commit/c9c5788a527b70d7f9…

[ci skip]

Previously these methods could return either a DateTime or a Time
depending on how the ActiveSupport::TimeWithZone instance had
been constructed. Changing to always return an instance of Time
eliminates a possible stack level too deep error in to_time where
it was wrapping a DateTime instance.

As a consequence of this the internal time value is now always an
instance of Time in the UTC timezone, whether that's as the UTC
time directly or a representation of the local time in the timezone.

There should be no consequences of this internal change and if
there are it's a bug due to leaky abstractions.

Mirrors the Time#subsec method by returning the fraction
of the second as a Rational.

Time instances can have fractional parts smaller than a nanosecond.

Mirrors the DateTime#sec_fraction method by returning the fraction
of the second as a Rational.