Add +variants to ActionView::FileSystemResolver documentation.
Merge pull request #17070 from felipecvo/master

Add +variants to ActionView::FileSystemResolver documentation.
Don’t require already required modules

abstract_unit.rb requires `action_controller` which [already includes the following lines of code](https://github.com/rails/rails/blob/64fcdce1d3a6a8768ab17f3be144270456814f82/actionpack/lib/action_controller.rb#L2L3):

```ruby
require 'abstract_controller'
require 'action_dispatch'
```
Merge pull request #17071 from claudiob/don-t-require-action-dispatch-twice

Don’t require already required modules
Preparing for 4.2.0.beta2 release
Add documentation about `config.action_dispatch.rescue_responses`

[ci skip]
Merge pull request #17076 from yuki24/write-doc-for-rescue-responses

Add documentation about rescue_responses in Configuring [ci skip]
[ci skip] fix typo in set examples
Merge pull request #17079 from y-yagi/patch-1

[ci skip] fix typo in set examples
some object allocation reduction for new AR objects

Benchmark:

```ruby
require 'objspace'
require 'active_record'

ActiveRecord::Base.establish_connection adapter: "sqlite3",
                                        database: ":memory:"

ActiveRecord::Base.connection.instance_eval do
  create_table(:articles) { |t| t.string :name }
end

class Article < ActiveRecord::Base; end
a = Article.create name: "foo"
a = Article.find a.id

N = 10
ObjectSpace::AllocationTracer.trace do
  N.times { Article.find a.id }
end
ObjectSpace::AllocationTracer.allocated_count_table
table.sort_by { |_,x| x }.each do |k,v|
  p k => (v / N)
end
```
Fix typo in AR changelog

- middlware -> middleware
Merge pull request #17080 from prathamesh-sonpatki/fix-typo-in-ar-changelog

Fix typo in AR changelog [ci skip]
Fix some typos in ActiveJob

[ci skip]
Merge pull request #17081 from prathamesh-sonpatki/fix-aj-typos

Fix some typos in ActiveJob
Fix typo in upgrading guide

- [ci skip]
- behvaior -> behavior
Merge pull request #17082 from prathamesh-sonpatki/fix-typo-in-upgrading-guide

Fix typo in upgrading guide
Make AJ integration tests much less verbose

In passing, avoid a blind retry in QC: instead, just fix the problem.
Tiny follow-up to #16999 [ci skip]

* Fix a typo
* Remove references to Rails version
* Remove an extra whitespace
Partition routes during setup.

Partitioning of all the routes is currently being done during the
first request. Since there is no need to clear the cache for
`partitioned_routes` when adding a new route. We can move the
partitioning of the routes during setup time.