[TASK] Remove group limit for FE and BE users

Group assignment for a backend- and frontend user
is currently limited to max. 20 groups per backend
user and max. 50 groups per frontend user.

The database field type for "usergroup" is now changed
to "text" so the group limitation can be removed.

Resolves: #93348
Releases: master
Change-Id: I93329a8c186e13439d68cc6c36345842c4edd929
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67577


Tested-by: core-ci <typo3@b13.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>