Consolidate clearing mImeInsetsFrozenUntilStartInput

As CL[1] that IMMS only invoke updateInputMethodTargetWindow when the
IME input target window changed, that caused somehow we can't clear
mImeInsetsFrozenUntilStartInput in ActivityRecord to make the activity
can receive IME insets correctly like when turning the screen off/on
and then unlocking the non-secure keyguard to back to the same app,
since the IME input target didn't changed.

Making sure IMMS side always invoke updateInputMethodTargetWindow to WM
to clear IME insets frozen state.

[1]: Id8a56c68a06a774ef12ba444fd9a368148ea4539

Fix: 205783849
Test: atest ActivityRecordTests#\
        testImeInsetsFrozenFlag_resetWhenReportedToBeImeInputTarget

Merged-In: I796754992911b917a49fcd18f22019c1eecad908
Change-Id: I796754992911b917a49fcd18f22019c1eecad908
(cherry picked from commit 5d580797)
Merged-In:I796754992911b917a49fcd18f22019c1eecad908