DO NOT MERGE Test sidecar OEM implementation for WM support library

This provides an example implementation of the Sidecar interface
for the Window support library, which allows mocking a foldable
device by reading its current configuration from settings.

This implementation also makes sure that the reported display
features are adjusted to the window position and coordinate space,
as required by the Sidecar interface contract.

The reported values can be updated by using the following shell
commands:
settings put global device_posture <posture>
settings put global display_features <type>-[<sX>,<sY>,<eX>,<eY>]

Bug: 146188055
Test: Manual, see instructions doc
Change-Id: I4764298d7633bc3ef574b5cbc2dee256e9cf3f03
(cherry picked from commit d66f77b0)