Add basic lifecycle transaction containers

This adds basic containers for holding some messages to a client,
that are related to activity lifecycle. Each transaction can hold
a list of callbacks and a final lifecycle state.

Some requests from ActivityManager to client that target activities
are now switched to use transactions. Scheduling, preparing and
executing a request is moved outside of ActivityThread class to
corresponding transaction items.

Bug: 64797980
Test: Existing AM CTS tests pass
Change-Id: I96df20787b3d792f655c9500e8a71032264d02cd