Ignore overriding pending animaiton for unlock transition.

System app can request to override app transition animation using
the following hidden APIs.

- IWindowManager#overridePendingAppTransitionRemote
- Activity#registerRemoteAnimations
- IActivityTaskManager#registerRemoteAnimationsForDisplay

We usually give the lowest priority for the overrides registered by
the last API, since it defines default transition animaiton for a given
transition type and others are used to overide more specific cases.

However remote animation for unlock transition is also used to sync
keyguard status between server_process and system ui, even system app
must not override it.

Bug: 231556392
Test: manual
  1. Press Power button to display the lock screen.
  2. Press Power button and the volume down button at the same time to
     take a screenshot.
  3. Tap the screenshot preview that appears in the lower left corner
     of the screen.
  4. Execute Fingerprint authentication to unlock the screen.
Change-Id: I16593c1aa7e7799e355aafbe47832e5c3b23c0cc