Add documentation on Active Job.

This adds documentation for the Active Job API. It includes
documentation on how to configure the queue_adapter, and how to create
new jobs. It adds links to the various other sections of the Active Job
documentation.
Merge pull request #17068 from mokhan/update-active-job-documentation

[ci-skip] Update Active Job API documentation
Disallow appended newlines when parsing as integer

\Z allows appended newlines where \z does not.
Merge pull request #17148 from mgenereu/patch-1

Disallow appended newlines when parsing as integer
Use #tr instead of #gsub where possible
[ci skip] add `test:jobs` task to testing guide
Fix style for rescue responses doc [ci skip]

 * Change 'Any ***s that are...' to 'Any *** that is...'
 * Fix style for default rescue_responses setting

This is a follow-up commit to:

 * https://github.com/rails/rails/pull/17076
 * https://github.com/yuki24/rails/commit/89b8836f2470c689f6b7d52cab3a418bb63aef26
Merge pull request #17151 from y-yagi/patch-1

[ci skip] add `test:jobs` task to testing guide
Merge pull request #17153 from yuki24/fix-doc-format-for-rescue-responses

[Railsguides] Fix style for rescue responses doc [ci skip]
Revert "Fix style for rescue responses doc [ci skip]"

Reason: There is a wrong newline, a typo, and the change
to singular is not good.

This reverts commit d76380cf1ccec7ffeff19827ae9b6d9b71327418.
minor fixes in the configuring guide [ci skip]
define hash on duration
Fix that a collection proxy could be cached before the save of the owner, resulting in an invalid proxy lacking the owner’s id.

Absent this fix calls like: owner.association.update_all to behave unexpectedly because they try to act on association objects where
owner_id is null.

more evidence here: https://gist.github.com/Empact/5865555
```
Active Record 3.2.13
-- create_table(:firms, {:force=>true})
   -> 0.1371s
-- create_table(:clients, {:force=>true})
   -> 0.0005s
1 clients. 1 expected.
1 clients updated. 1 expected.
```

```
Active Record 4.0.0
-- create_table(:firms, {:force=>true})
   -> 0.1606s
-- create_table(:clients, {:force=>true})
   -> 0.0004s
1 clients. 1 expected.
0 clients updated. 1 expected.
```
Merge pull request #17160 from lsylvester/duration-hash

define hash on duration
add notes for `define_model_callbacks` [ci skip]
Merge pull request #17167 from kuldeepaggarwal/doc-define_model_callbacks

add notes for `define_model_callbacks`
Fix typo
Merge pull request #17168 from jwworth/task/fix_typo

Fix typo [ci skip]
fix typo in in define_model_callbacks comment [ci skip]
Merge pull request #17172 from rselk/typo

fix typo in in define_model_callbacks comment [ci skip]