[BUGFIX] Enable default action in backend user module

The last used action is now properly resolved
again in the backend user module. Due to the
fact that accessing the module, extbase always
uses `index` as the selected action, the stored
user state was never resolved.

This is now fixed by using the index action
as forward action, forwarding to either the
stored default action or falling back the
new "listAction" which now acts as the main
entry point.

Resolves: #103692
Releases: main, 12.4
Change-Id: I764d130dc1a53a8fed25dadfaecaab5dd4eb58de
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84252


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Andreas Kienast <a.fernandez@scripting-base.de>
Tested-by: Andreas Kienast <a.fernandez@scripting-base.de>