Fix IME insets animation stucked by wrong InsetsHint

There is a chance that if InsetsSourceProvider#updateControlForTarget
invoked when its serverVisible not yet visible, then the insetsHint of
the new InsetsSourceControl will be empty because CL[1] will set
insets source frame as empty when the serverVisible is false.

This would make the insetsHint of the control may not able to get
updated if the source frame size is same as the last visible source
frame in the next onPostLayout, that affects the insets animation
will not fullly animated because of wrong InsetsHint.

Add a mInsetsHint field in InsetsSourceProvider to strore the last
insetsHint from onPostLayout for initializing the new source control.

[1]: Ie7845de2830cdbdfd0049b8eef5a5f0704f796e8

Fix: 230581950
Bug: 229938982
Test: manual as issue steps.
Test: atest InsetsStateControllTest#testGetInsetsHintForNewControl
Change-Id: I0fd5845d1f816b558deeed490c93ec207e2f0607