Feature: #107783 - Register metadata extractors via interface 

See forge#107783

Description 

Metadata extractors are service classes that are automatically executed whenever an asset or file is added to the FAL storage, or FAL indexing is executed.

Registration of metadata extractors now happens automatically when the required interface ExtractorInterface is implemented by the class, utilizing autoconfigure tagging provided by the Symfony Dependency Injection framework.

No further manual registration is required.

Additionally, the class ExtractorRegistry now uses strong type declarations, which should not affect public consumers. The interface remains unchanged in its type declarations.

Impact 

Instances of ExtractorInterface are now detected and registered automatically.