This is a variant implementation of the changes proposed in #19914.
Unlike that PR, the change in behavior is isolated in its own class.
This is to prevent wonky behavior if a Proc is assigned outside of the
default, and it is a natural place to place the behavior required by #19921
as well.

Close #19914.

[Sean Griffin & Kir Shatrov]

config.static_index configures directory Index "index.html" filename

Remove unused package tasks

removed erroneous line. Corrected presence validation example.

Addresses #20343.
Removes erroneous line of code in the sample codeblock.

[ci skip] Fix block parameter of assert_no_difference

Deprecate `:nothing` option for render method

`head` method works similar to `render` method with `:nothing` option

Give credit to extra contributor for Base.reload fix

Set `config.static_index` to serve a static directory index file not
named `index`. For example, to serve `main.html` instead of `index.html`
for directory requests, set `config.static_index` to `"main"`.

We are using `all:build` now.

Properly append preload / includes args on Merger

Couldn't find other way to get the association name from a given class
other than looping through `reflect_on_all_associations` reflections ..

Noticed this one while looking at this example:

```ruby
class Product < ActiveRecord::Base
  has_many :variants
  has_many :translations
end

class Translation < ActiveRecord::Base
  belongs_to :product
end

class Variant < ActiveRecord::Base
  belongs_to :product
end

class BugTest < Minitest::Test
  def test_merge_stuff
    product = Product.create! name: 'huhu'
    variant = Variant.create! product_id: product.id
    Translation.create! locale: 'en', product_id: product.id

    product_relation = Product.all
                              .preload(:translations)
                              .joins(:translations)
                              .merge(Translation.where(locale: 'en'))
                              .where(name: 'huhu')

    assert_equal variant, Variant.joins(:product).merge(product_relation).first
  end
end
```

Remove custom `lines` and use `/tools/line_statistics`

SQLite3: Add collation support for string and text columns

Add application/vnd.api+json alias to the JSON MIME Type.

Allow the use of symbols or strings to specify enum values in test fixtures

Cause ActiveRecord::Base::reload to also ignore the QueryCache.

If specify `strict: :default` explicitly, do not set sql_mode.

Currently, values for columns backing Active Record enums must be
specified as integers in test fixtures:

    awdr:
      title: "Agile Web Development with Rails"
      status: 2

    rfr:
      title: "Ruby for Rails"
      status: <%= Book.statuses[:proposed] %>

This is potentially confusing, since enum values are typically
specified as symbols or strings in application code. To resolve the
confusion, this change permits the use of symbols or strings to specify
enum values:

    awdr:
      status: :published

It is compatible with fixtures that specify enum values as integers.

Changed mysqldump to include sprocs and functions

Fix rake method definition leaking onto Object

This is a leftover of #19867

[PoC] Stop shadowing parameters named `action`

Remove redundant 'Rails' from Rails::AppRailsLoader constant

[ci-skip] Replace dead link about HttpOnly cookies.

add framework_test

add another test

Add assertion for get? method into test cases

Fix indentation warning on active_support ordered_options

Remove unnecessary reference to example Blog app in initialization guides

Remove web-console and spring from test group on default Gemfile.