[FEATURE] Introduce PHP attribute based backend controller registration

Backend controller had to be registered in the extension
`Services.yaml` file with tag `backend.controller`.

This change enables automatic service registration with
the tag `backend.controller` attached to it by using the
newly introduced `\TYPO3\CMS\Backend\Attribute\Controller`
PHP attribute. Thus providing a additional and simpler
way, without deprecating or enforcing to change already
existing registrations.

Releases: main
Resolves: #99055
Change-Id: I9b07d315f766f95dc22dd5a3db9b3bf7efcef4fc
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76537


Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>