Use bugfix flags for desktop transitions: enter, exit, alttab, applaunch

The transitions changes are bug fixes / polish, so use bugfix flags
for these changes.
An existing non-bugfix flag cannot be changed into a bugfix flag, so
instead we create new flags with the bugfix type.

Also fix a bug where enter-transitions were using the old flag
(enableDesktopWindowingTransitions) instead of the new one
(enableDesktopWindowingEnterTransitions).

Bug: 380224875
Bug: 380224768
Bug: 380225486
Bug: 380224832
Test: manual - disable original flags, use bugfix flags
Flag: com.android.window.flags.enable_desktop_windowing_enter_transition_bugfix
Change-Id: I084b8a5489d39b6bf57e791ba04e65f0f0ebd8df