[TASK] Deprecate AbstractUserAuthentication->fetchUserRecord

To untie authentication services from user authentication a bit better,
the fetchUserRecord() method of AbstractAuthenticationService now
implements fetchUserRecord() on its own instead of calling the method
with the same name of $pObj.
AbstractUserAuthentication->fetchUserRecord() is then unused and can
be deprecated.

Resolves: #86466
Releases: master
Change-Id: Ia144ea2dfb8a7c7462ed12875ee35caab9763ba2
Reviewed-on: https://review.typo3.org/58485


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>