Create a type for tracking chains of Actions requested of WM

Introduces a new type ActionChain which, when linked together,
represent a sequence of related actions WM performed as part
of a Transition.

When performing a larger "logical" operation (eg. launching
an activity), it is made up of several asynchronous actions (eg.
ask current activity to pause; on paused, start new activity and
wait for drawn, ask Shell if more work needs to be done, etc.).

Because these are async, we need to track these sets of actions
independent of actions from another "logical" operation otherwise
WM is unable to distinguish them. Today this DOESN'T happen and
thus we currently occasionally combine multiple logical operations
into one Transition which both confuses Transition clients (shell)
and can contribute to latency (unrelated operations waiting for
eachother).

This type is the primary component used to solve this problem. A
new "Action" will started at every IPC entry-point into WM. This
will be linked to a prior Action which caused this one to exist.
These linked actions form a chain of actions tracking the causes
and effects of each step in executing a Transition. This object
is then plumbed from the entry-point down (into synchronous
logic), so that any resulting changes to WM can be associated
with the that action chain.

In this CL, only the type was added and then used to wrap the
direct transition entry-points. Functionally, nothing changes
as the "default" behavior when starting an action chain is
equivalent to the current behavior (use collecting transition
if available, otherwise use nothing).

Bug: 325114242
Test: New class added but no functional changes, so existing tests
Flag: com.android.window.flags.transit_tracker_plumbing
Change-Id: I7a7e0730437fc1a15e44a55a84fea33aa72f1301