Small Action View Overview edits [ci skip]

Some small grammar and readability edits
Define the Duration#instance_of? method

Since Duration is extending from ProxyObject which extends itself from
BasicObject, the Duration object doesn't respond to the #instance_of?
method. Thus, the #method_missing hook get triggered, delegating the
method to its `value` attribute.

However, Rubinius' #eql? definition relies on #instance_of?, thus this
will equal to true with a Fixnum (since its `value` attribute is a
Fixnum) while it should not.

The previous behavior was wrong anyway, no matter the implementation.
Grammar pass

[ci skip]

Add improvements from @eileencodes [skip ci]
provide a builder for form labels to customize wrapping around I18n content
Point release notes to stable branch for list of commits. [ci skip]
Same as f39cb2b except backport friendly

Point release notes to stable branch for list of commits. [ci skip]
Same as f39cb2b except backport friendly

Point release notes to stable branch for list of commits. [ci skip]
[ci skip] Added documentation for has_many scope parameter
Fix a few typos/some grammar in Active Job Basics
Merge pull request #16590 from loganhasson/master

[ci skip] Fix typos/grammar in Active Job guide
[ci skip] correct docs about the migration generation
Merge pull request #16592 from aditya-kapoor/fix-migration-docs

[ci skip] correct docs about the migration generation
[ci skip] add doc for STEP in migration
Merge pull request #16575 from tomkadwill/added_has_many_scope_documentation

[ci skip] Added documentation for has_many scope parameter
Merge pull request #16593 from aditya-kapoor/add-doc-for-step

[ci skip] add doc for STEP in migration
[ci skip] Fix Active Job grammar in api docs
Merge pull request #16594 from loganhasson/master

[ci skip] Fix Active Job grammar in api docs
Remove timestamp type from generator usage

It was soft removed at 03035d69e14032a589e9653e3145237b8a9a09be
Make the explicit the Active Job dependency of Action Mailer
Update configuring.md [ci skip]

Remove ActiveRecord config instructions for active_record.attribute_types_cached_by_default, which was removed in https://github.com/rails/rails/commit/66736c8e50585