fix order dependent test in AggregationsTest

Ensure class variable is set to nil.

It prevents the following test to fail:

    def test_do_not_run_the_converter_when_nil_was_set
      customers(:david).non_blank_gps_location = nil
      assert_nil Customer.gps_conversion_was_run
    end

Check https://github.com/rails/rails/blob/master/activerecord/test/models/customer.rb#L7
for more information.
Let's run action pack tests with Dalli

There is no memcache gem left in repo.
More fixes for action pack tests with Dalli.
Merge pull request #7451 from frodsan/fix_dep_ag

fix order dependent test in AggregationsTest
fix order dependent test in AR::BasicsTest

This test https://github.com/rails/rails/blob/master/activerecord/test/cases/base_test.rb#L381
is failing because is not setting `CreditCard.pluralize_table_name` to `false`.

In this case, i prefer to change to another model that is not in the `GUESSED_CLASSES`
array.
ensures that the test repairs the validation setup
Merge pull request #7460 from frodsan/fix_nested_attributes_test

ensures that the test repairs the validation setup
Remove dependency on actionpack in ActionView::AssetPaths

Since Action View should not depend on actionpack, it's best to delegate
invalid_asset_host! to controller and just rely on such simple contract
instead of raising ActionController::RoutingError directly.
Move ActionController::RecordIdentifier to ActionView

Since it's more about DOM classes and ids it belongs to Action View
better. What's more, it's more convenient to make it part of Action View
to follow the rule that Action Pack can depend on Action View, but not
the other way round.
Add ActionView::ModelNaming

It's just a duplicate of ActionController::ModelNaming. These are just a
simple helpers for decoupling Active Model, so it does not make sense to
extract it to Active Support, but the point is to decouple also Action
View and Action Pack
Deprecate ActionController::RecordIdentifier
Move action_controller/vendor/html-scanner to action_view

This is another step in moving Action View's dependencies in Action Pack
to Action View itself. Also, HtmlScanner seems to be better suited for
views rather than controllers.
Remove stubs from LogSubscriber tests

We can use another way to instantiate ActionView::Base, by passing
renderer as a first option. Thanks to that we can just pass prefixes to
LookupContext instead stubbing them on the controller. This is also good,
because that kind of API is used in Rails code.
Remove comment about getting rid of old AV::Base.new behavior

I've talked to José Valim, who added this comment, and there is no need
to remove old API. It's good to have a simple way to instantiate
ActionView::Base, by just passing view paths as a first argument,
instead of constructing LookupContext and then the Renderer.

[ci skip]
Deprecate mime types lookup in auto_discovery_link_tag

Automatically handling mime types for things other than :rss and :atom
is not functionality that justifies dependency on Mime::Type from
actionpack.
Remove Mime::Type translations from Action View

Action View should not be responsible for translating mime types. Any
translation that's needed should be handled at controller level.
Add ActionView::Base.default_formats

default_formats array is used by LookupContext in order to allow
rendering templates when :formats option is not passed. Previously it
was always set to Mime::SET, which created dependency on Action Pack. In
order to remove this dependency, Mime::SET is used only if
ActionController is loaded.
Use ActionView::Base.logger instead of AC::Base.logger
Don't require action_dispatch in ActionView::UrlHelpers

ActionDispatch::Routing::UrlFor was always required in UrlHelpers. This
was changed by splitting previous implementation of UrlHelper into 2
modules: ActionView::Helpers::UrlHelper and
ActionView::Routing::UrlHelper. The former one keeps only basic
implementation of url_for. The latter adds features that allow to use
routes and is only required when url_helpers or mounted_helpers are
required.
Implement ActionView::Template::Types

AV::Template::Types is a small abstraction to allow to specify template types
that can be used in ActionView. When Action Pack is loaded it's replaced with
Mime::Type.