Remove IMMS#mShowRequested

Now we have ImeTargetWindow#isRequestedImeVisible as per-window state,

To avoid this global visible state may cause some system controlled IME
visiblity issues, replace mShowRequested with
IMMS#isShowRequestedForCurrentWindow() to get the requested IME visible
state from the current focused window.

Also, in case in IMMS side may not be able to restore the IME visibility
when the activity got relaunched, updates AR#mLastImeShown state when
relaunching the activity without preserving window, and modifies
shouldRestoreImeVisiblity(windowToken) for IMMS to restore the last IME
visiblity state for that relaunching activity window.

Bug: 246309664
Test: atest InputMethodVisibilityControlTest
Test: atest CtsInputMethodDeviceTests
Change-Id: I9e69043d4aeaa2931ea192692007c7ca6420a107