[META] Adjust parameters in interfaces

Problem/Motivation

During the previous major, some methods in interfaces were preliminarily added or typehinted by adding inline comments in place of the to-be real parameters. This allows Symfony's debug classloader to report deprecations for methods that do not implement the stealth parameters, i.e. the concrete classes will throw implementation errors even if the interfaces are not yet formally enforcing the signatures.

The following interfaces need to be adjusted prior to 12.0.0:

• \Drupal\Core\File\FileSystemInterface
• TBA

Steps to reproduce

grep for function.*\*

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet