Removed support for deprecated `counter_sql`

Removing not useful test related to reflect_on_all_associations

update test names in testing guide [ci-skip]

The comment in the test pretty much summarizes the issue.
`FIXME these assertions bust a lot`

Adding any type of association in class `Firm` will break this test.

I removed some deprecated stuff and this test failed.

I do not think this test provides any useful value. First of all who
counted last that 39 is the right number of associations.

Secondly there are a large number of tests which depend on reflection
returning right information about associations. Those tests will start
failing if there is a bug in the code.

Remove deprecated `Date#to_time_in_current_zone`

Remove deprecated `config.whiny_nils`

Remove `page_cache_extension` method

Do not invoke callbacks when delete_all is called

Conflicts:
	activerecord/CHANGELOG.md

calling default_scope without a proc will raise ArgumentError

Calling default_scope without a proc will now raise `ArgumentError`.

Remove AR::Connection#clear_stale_cached_connections! deprecated method

Removed deprecated method type_cast_code from Column

Use native Array#uniq and Array#uniq! instead.

  ActionController::AbstractRequest  => ActionDispatch::Request
  ActionController::Request          => ActionDispatch::Request
  ActionController::AbstractResponse => ActionDispatch::Response
  ActionController::Response         => ActionDispatch::Response
  ActionController::Routing          => ActionDispatch::Routing
  ActionController::Integration      => ActionDispatch::Integration
  ActionController::IntegrationTest  => ActionDispatch::IntegrationTest

Removed deprecated options for assocations

Deprecated options `delete_sql`, `insert_sql`, `finder_sql` and `counter_sql`
have been deleted.

Commit cfa35c55 removed the
buffered_logger from AS, which required the logger file. Now we need to
add the proper require here.

Remove `FormBuilder` deprecation warning about block argument and tests