Properly manage newly required parameter of FileUsageBase::__construct()

Problem/Motivation

Constructor has @deprecated tag and shouldn't.

it should trigger an error if the parameter is missing.
Additionally, DatabaseFileUsageBackend extends this class, and $config_factory is an optional third parameter in that class.

Proposed resolution

Remove @deprecated tag from FileUsageBase Constructor
Maintain the current BC layer and trigger an error if $config_factory is missing
Reorder the constructor arguments of DatabaseFileUsageBackend so that $config_factory is first and required.
Provide a BC layer if the arguments are passed in the old order and trigger an error.
Provide legacy tests to test the error triggering and that the BC layers work.
File a CR on the changing parameter order of DatabaseFileUsageBackend
File a follow-up against drupal 9 to restore type-hints and required status to parameters of both classes

Remaining tasks

review
commit

User interface changes

none

API changes

The signature of DatabaseFileUsageBackend has changed. A BC layer has been provided.

Data model changes

none

Release notes snippet

The constructor of DatabaseFileUsageBackend has had the order of its parameters changed.