[ci skip] Add ImageMagick to ActiveStorage dependencies

In order to run ActiveStorage's tests successfully, you need
imagemagick.

Add usage of procs without arguments to callbacks guide

Make `rake routes` deprecate before deleting

Improve Active Job test helpers

The `Relation::Merger` has a problem that order values would be merged
as nested array.

That was caused an issue #33664 since if array value is passed to
`order` and first element in the array includes `?`, the array is
regarded as a prepared statement and bind variables.

https://api.rubyonrails.org/classes/ActiveRecord/Sanitization/ClassMethods.html#method-i-sanitize_sql_for_order

Just merging that as splat args like other values would fix the issue.

Fixes #33664.

Fix `rails routes -c` for controller name consists of multiple word.

Improve tests for ActiveRecord::ConnectionAdapters::ConnectionPool co…

Example:
```
def test_assert_performed_with
  MyJob.perform_later(1,2,3)

  perform_enqueued_jobs

  assert_performed_with(job: MyJob, args: [1,2,3], queue: 'high')
end
```

Follow up #33626.

Execution of `assert_performed_jobs`, and `assert_no_performed_jobs`
without a block should respect passed `:except`, `:only`, and `:queue` options.

Note that it removes changelog entry of #33265 since the entry in this commits
includes that too.

If the `:queue` option is specified, then only the job(s) enqueued to a specific
queue will not be performed.

Example:
```
def test_assert_no_performed_jobs_with_queue_option
  assert_no_performed_jobs queue: :some_queue do
    HelloJob.set(queue: :other_queue).perform_later("jeremy")
  end
end
```

If the `:queue` option is specified, then only the job(s) enqueued to a specific
queue will be performed.

Example:
```
def test_assert_performed_jobs_with_queue_option
  assert_performed_jobs 1, queue: :some_queue do
    HelloJob.set(queue: :some_queue).perform_later("jeremy")
    HelloJob.set(queue: :other_queue).perform_later("bogdan")
  end
end
```

Set
````
queue_adapter.perform_enqueued_jobs = true
queue_adapter.perform_enqueued_at_jobs = true
queue_adapter.filter = only
queue_adapter.reject = except
queue_adapter.queue = queue
```
if block given.
Execution of `flush_enqueued_jobs` doesn't require that.

Add missing documentation option to number_to_currency

[ci skip]

`rake routes` was a public task. Therefore, I think that we should deprecate
it before deleting it.

Related to #32121.

Update guide to mention code linters available

If the `:queue` option is specified, then only the job(s) enqueued to
a specific queue will be performed.

Example:
```
def test_perform_enqueued_jobs_with_queue
  perform_enqueued_jobs queue: :some_queue do
    MyJob.set(queue: :some_queue).perform_later(1, 2, 3) # will be performed
    HelloJob.set(queue: :other_queue).perform_later(1, 2, 3) # will not be performed
  end
  assert_performed_jobs 1
end
```

Follow up #33265

[bogdanvlviv & Jeremy Daer]

Commands generally prefer say to puts.

Improve test case to test enum correctly

Move the initializers rake task to Rails::Command

activestorage: yarn build

Fixes #33520.

without define the enum in class “SpecialBook”, any string status will be casted to integer 0. Then the test have no meaning.

[Rich Chen]

DRY in Active Record Query Interface [ci skip]

Context https://github.com/rails/rails/pull/33413#issuecomment-414137587

The sentence "This is exactly the same as defining a class method ..."
is not true, so #33653 fixed it, but added changes repeat what is explained
a few lines below. We can remove this part since a user is able to get info
about the difference between scopes and class methods below.

Context https://github.com/rails/rails/pull/33653#discussion_r211105969.

Reverts #33653, 97feb499.

Explained difference between scope & class method

Now requires version 1.11 or newer. Ref: bf5f41d9

This test no longer covers the behavior of ActiveStorage::PurgeJob. Attached blobs are ignored by ActiveStorage::Blob#purge as of 934fccd5, which includes an equivalent model test.

https://travis-ci.org/rails/rails/jobs/417783260#L1173-L1179