Moved onStackExpandChanged() out of the onImeHidden Runnable.

This is an attempt to fix b/435098356 where shell does not properly
notify system of bubble bar is collapsed.

Moved onStackExpandChanged() out of the onImeHidden Runnable in
BubbleStackView.

Also call onStackExpandChanged(false) on BubbleController.setSysuiProxy
to handle case if shell has crashed while bubbles stack was expanded.

Fixes: 435098356
Flag: com.android.wm.shell.fix_bubbles_expanded_sysui_flag
Test: Manual. Checked that b/391909607, b/379474417 & b/432344114 not
reproducing with this change.

Change-Id: Iac0f251b638fcf27c676b4ae3ad2c5cac1249267