[BUGFIX] Unittest failure: Tx_Phpunit_FrameworkTest::loginUserIsZeroAfterCreateFakeFrontEnd

Since 6.2 the AbstractUserAuthentication uses real boolean values for
loginUser.

Adapt the test to run only in <6.2 and create a new test for >= 6.2.

Resolves: #59955
Change-Id: I9b43b4a768a7696dbd009848c6004150b8042148
Reviewed-on: https://review.typo3.org/31177
Reviewed-by: Oliver Klee
Tested-by: Oliver Klee