Fix WallpaperWindowToken visible update with Shell transition

With Shell transition, when mVisibleRequested is changed, it will wait
until the transition finish to update the isVisible(). As a result, if
there is a visible change before the previous transition is finished,
it will be skipped.

For example, when we first open a fullscreen app and then immediately
enter pip:
1. TRANSIT_OPEN will call to hide wallpaper and set mVisibleRequest to
false, but not commit visible until transition animation is finished.
2. TRANSIT_PIP will call to show wallpaper, but if it is started before
the OPEN transition is finsihed, it will not update the wallpaper
mVisibleRequested, which will leave the wallpaper hidden.

Fix: 210965575
Bug: 210965692
Test: atest WMShellFlickerTests:ExpandPipOnDoubleClickTest
Change-Id: I2578aafd024a3c9a6ec96079d4dc6cb740c890d2