Disable LayoutTransitions for transient taskbar.

Taskbar stashes once an app is launched from taskbar, or remains stashed if you launch something from All Apps. The layout transitions therefore are unlikely to be seen by the user. Disabling them means when the user unstashes, they will see the end result of the transition immediately. The problem with them being enabled for transient taskbar is we set icon alpha to 0 if Taskbar is stashed, which conflicts with the alpha layout transition animation.

Flag: com.android.window.flags.enable_taskbar_recents_layout_transition
Fix: 406809935
Test: Manual
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:c0af778af1bf99e3536450c6ecc054d1d8d44953)
Merged-In: Ibcfc04e5c9af104725a69c8cceccef49544d7bd3
Change-Id: Ibcfc04e5c9af104725a69c8cceccef49544d7bd3