[AChoreographer] Split source files out from libandroid.

This change is prework for allowing HWUI to depend on AChoreographer so
that the dependency on DisplayEventReceiver is decoupled. AChoreographer
needs to be split out from libandroid, as libandroid transitively
depends on libhwui causing a circular dependency otherwise.

Bug: 136262896
Test: builds
Change-Id: Id60f9801cd82314065d82462e2a4286a3cb91e98