Follow-up to #39344.

This adds back coverage of `collection_select`, adds new coverage of
`collection_radio_buttons`, revises existing coverage of
`collection_check_boxes`, and unifies these sections.

Follow-up to #39344.

Adds back mention of `text_area` helper.

It is a super edge case but the alias should be resolved before
`clear_attribute_changes` since `clear_attribute_changes` is not aware
of attribute aliases.

Redundant `to_s` has a few overhead. Especially private methods are not
intend to be passed user input directly so it should be passed always
string.

Removing redundant `to_s` makes attribute methods about 10% faster.

```ruby
ActiveRecord::Schema.define do
  create_table :users, force: true do |t|
  end
end

class User < ActiveRecord::Base
  def fast_read_attribute(attr_name, &block)
    @attributes.fetch_value(attr_name, &block)
  end
end

user = User.create!

Benchmark.ips do |x|
  x.report("user._read_attribute('id')") { user._read_attribute("id") }
  x.report("user.fast_read_attribute('id')") { user.fast_read_attribute("id") }
end
```

```
Warming up --------------------------------------
user._read_attribute('id')
                       272.151k i/100ms
user.fast_read_attribute('id')
                       283.518k i/100ms
Calculating -------------------------------------
user._read_attribute('id')
                          2.699M (± 1.3%) i/s -     13.608M in   5.042846s
user.fast_read_attribute('id')
                          2.988M (± 1.2%) i/s -     15.026M in   5.029056s
```

Promote `clear_attribute_change` as attribute methods

Do not mark attributes as changed when the type is case insensitive a…

Do not mark Postgresql MAC address and UUID attributes as changed when the assigned value only varies by case.

Fix Rubocop warnings.

Fix merge conflict error.

Fix merge conflict error.

For now, `increment` with aliased attribute does work, but `increment!`
with aliased attribute does not work, due to `clear_attribute_change` is
not aware of attribute aliases.

We sometimes partially updates specific attributes in dirties, at that
time it relies on `clear_attribute_change` to clear partially updated
attribute dirties. If `clear_attribute_change` is not attribute method
unlike others, we need to resolve attribute aliases manually only for
`clear_attribute_change`, it is a little inconvinient for me.

From another point of view, we have `restore_attributes`,
`restore_attribute!`, `clear_attribute_changes`, and
`clear_attribute_change`. Despite almost similar features
`restore_attribute!` is an attribute method but `clear_attribute_change`
is not.

Given the above, I'd like to promote `clear_attribute_change` as
attribute methods to fix issues caused by the inconsisteny.

Make custom inspect methods more consistent

Fix issue with expression index in insert_all

Based on the docs which state unique_by option of insert_all can use the
index name if desired, one would expect the method to work normally and
use the `unique_by` option to determine duplicates.

However, there's an issue where the insert_all expects a Set instead
of the string representing the index expression it is given. This causes
an error. Returning the string expression instead of attempting to
format it works perfectly though.

Replace 'Stubs out' with 'Generates' in generator USAGE's [ci skip]

Alias direct_descendants as subclasses

Generators generate things, but what is meant by 'Stubbing out' might
confuse beginners and non-native English speakers.
While generated tests are stubs that should have an implementation, a
generated model is a valid model that doesn't require any changes.

This alias overrides Class#subclasses.  Thus calls to `subclasses` get a
free performance boost when the class extends DescendantsTracker.

Support attribute aliases for `type_for_attribute`

Ensure column names on reflection as a string

Use `join_primary_key` and `join_foreign_key` directly.

Similar with #39496.

If association column names are defined as a symbol, association access
will cause `Symbol#to_s` each time since attributes and columns hash
keys are a string.

To avoid that extra `Symbol#to_s` allocation, ensure column names on
reflection as a string.

`has_attribute?` should be aware of attribute aliases

Related to #39495.

For now, `read_attribute`, `write_attribute`, `[]`, `[]=` are aware of
attribute aliases, but `has_attribute?` is not. It will easily miss
attribute alias resolution before using `has_attribute?`, it is very
inconvenient.

I think the inconvenience is not intended, so `has_attribute?` should be
aware of attribute aliases like as others for consistency.

Allow attribute aliases for `validates_uniqueness_of`

Fix test name that no longer raises exception

Use size == 1 instead of one? to check hashes count in HashWithIndifferentAccess#update

This is most easiest done by switching to before_setup, which fits since
we're also testing the ordering of the reset calls provided by the
TestHelper.

Don't recommend disabling CSRF protection [ci skip]

Reset ActiveSupport::CurrentAttributes even where executor doesn't wrap

The previous example disables CSRF protection for JSON format requests,
which allows any request to bypass it by adding the right Accept header.

Accept is one of the few headers that doesn't trigger a CORS preflight:
https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#Examples_of_access_control_scenarios

Instead of disabling it entirely, the simple case where authentication
is handled without a session (e.g. when using API keys) can be solved by
switching to the `:null_session` strategy.

For more complex cases (e.g. an API that uses session authentication),
I don't think a copy-and-paste-able example is appropriate; the user
needs to understand CSRF protection in order to make an informed choice.

AD::Static refactor with precompressed Brotli support

When using an external build process (webpack, grunt) it's helpful for
rails to be able to serve those assets. Brotli has better compression
than gzip and should eventually replace it for static assets.

When using an external build process (webpack, grunt) it's helpful for
rails to be able to serve those assets. Brotli has better compression
than gzip and will eventually replace it for static assets.

Added link to infosec.mozilla.org under the security guide [ci skip]