[TASK] PSR-12: Add empty lines at the beginning of PHP files

This change adds two changes
        'blank_line_after_opening_tag' => true,
        'single_trait_insert_per_statement' => true,

to our PHP-CS Fixer configuration, adopting more rules related
to PSR-12.

Resolves: #91020
Releases: master
Change-Id: I180b2cbceb077911bddeb42d9f131e5b32244ed2
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64158


Tested-by: Josef Glatz <josefglatz@gmail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Alexander Schnitzler <git@alexanderschnitzler.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: TYPO3com <noreply@typo3.com>
Reviewed-by: Josef Glatz <josefglatz@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Alexander Schnitzler <git@alexanderschnitzler.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>