Handle replacement of StatusChips in SystemStatusAnimationScheduler

This CL contains a refactoring of SystemStatusAnimationScheduler to allow cancellation of StatusEvents in order to replace them with higher priority status events. Because the DelayableExecutor does not provide any cancellation functionality, I replaced the Executor based logic of scheduling animations with coroutines.

Additionally, prepareChipAnimation() (in SystemEventChipAnimationController) does no longer need to be called one layout pass before the chip appear animation is started. The appear animation can now be started immediately after calling prepareChipAnimation().

Both changes are only in effect when the PLUG_IN_STATUS_BAR_CHIP flag is enabled.

Bug: 197638244
Test: separate CL (ag/20982130)
Change-Id: Ice296b0b9950d6ceac83aa8df7652552acfdf971