Feature: #102951 - Provide PSR-7 request in Extbase validators

See forge#102951

Description

Extbase abstractValidator now provides a getter and a setter for the PSR-7 Request object. Validators extending AbstractValidator will include the PSR-7 request object, if the validator has been instantiated by Extbase ValidationResolver.

Impact

Extension developers can now create custom validators which consume data from the PSR-7 request object (e.g. request attribute frontend.user).