Use less iterations for KeyGenerator in tests

update 4_2_release_notes

Correctly detect mutation on serialized columns mapping to binary

[ci skip] Fix typo of `collection_singular_ids=` method.

[ci skip] Fix typo of `collection=` method.

Fixes #16701

Fix spelling. [CI SKIP]

This was caused by #15327.

Update documentation to match change in #5942 [ci skip]

This commit improves performance of cookie tests:

Ruby  |   After  |   Before
----- | --------:| --------:
MRI   |    5.03s |     9.28s
JRuby |   25.45s |  1648.23s

Please note the improvement for JRuby.

[ci skip] Modify a web-console PR link for release noted

[ci skip] Updated documentation syntax of other parameter for rdoc

Adjusted punctuation and grammar for Form Helpers guide [ci skip]

[ci skip] Updated documentation syntax of block parameter for rdoc

[ci skip] Updated include to reference record parameter for rdoc

[ci skip] Updated documentation syntax of block parameter for rdoc

[ActiveJob] Autoload adapters

Speed up JRuby tests by improving the startup time

Otherwise, it's possible for GC to run in between, and fail the test.

[ci skip] Added documentation for has_and_belongs_to_many extension parameter

Cache the value of `changed_attributes` when calling `changes_applied`

* Also duplicated find_by tests from relations_test.rb to finder_test.rb now
	that we have a completely different implementation on the class (in core.rb
	with AST caching stuff).

* Also removed a (failing) test that used mocks. Now that we have tests for the
  behavior, there's no point having another test that tests the implementation
	(that it delegates). Further, what the test was implying is nolonger true with
	the current implementation, because Class.find_by is a real method now.

Added web links

Added web links to resque, delayed_job and sidekiq

[ci skip] make assert messages consistent

Use ActiveSupport::Concern