Separate out locked part of setLockScreenShown

This is now used "internally" (via windowOrganizerController) and
that already holds the lock and doesn't need permission checks.

For the sake of chain tracking, this also means we need to be able
to track internal calls through here synchronously.

Bug: 325114242
Test: N/A
Flag: EXEMPT mechanical refactor
Change-Id: I4752a08bf4bd2c3f703b556b498c47355271d465