Add fallback transition player

Adds a fallback transition player which basically acts
a simple "forwarder". This is intended to be used during
startup or during periods of sysui being crashed.

Bug: 365884835
Test: existing tests since they automatically use this
Flag: com.android.window.flags.fallback_transition_player
Change-Id: I57bc45aa2924b402ac89e34a23fea997e498f0e7