[TASK] Deprecate fe_users & fe_groups TSconfig

TSconfig plays an important role in the Backend:
It configures rendering and behavior details in
the Backend and can be set on pages, be_users and
be_groups field, leading to UserTsConfig and
PageTsConfig.

Frontend users and Frontend groups have this
as well on database level, together with an
API in class FrontendUserAuthentication. This
was probably added in the old days to allow a
similar thing as Backend TSconfig for Frontend
users as well. It is however unused by the core
and there seems to be only a very limited number
of extensions that ever used this. Developers
think of "TSconfig" as Backend specific things,
and that's how it should be.

To reduce confusion, the patch deprecates the
TSconfig database fields in fe_groups and fe_users
table along with the PHP API.

Resolves: #99075
Releases: main
Change-Id: I599670bf5e87eee4aa5e1ba353da1e7dc9351702
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76578


Tested-by: core-ci <typo3@b13.com>
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: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>