Let work profile unlock screen force the work-profile IME

On the work profile unlock screen, the work profile IME isn't
unlocked yet. Yet, we want to apply the restrictions that the
work profile has applied, such that the work profile password
isn't entered into an IME that the work profile didn't allow.

Bug: 139872425
Test: atest CtsInputMethodTestCases
Flag: android.view.inputmethod.enforce_device_policy_ime

Change-Id: I462cd23b55eb863bd8131c6beee90704192dcff0