Update SidecarProvider to pass Application Context.

Use Application Context in SidecarProvider to avoid a memory leak. There
is a memory leak when an Activity is used that does not handle
configuration changes. The leak happens because the Activity may be
captured and retained longer than desired.

Bug: 202989046
Bug: 202250276
Test: manual - Use an activity that ignores configuration changes.
Test: Install leak canary.
Test: Subscribe to WindowLayoutInfo changes using an Activity.
Test: Rotate the device a few times.
Change-Id: I953d0cb39d21af00aad7044678e256d16b2d1c85