Use MediaSession remote actions

Defaults to using MediaSession actions in pip menu when UMO
experience flag is turned on. This also adds the MediaSession
fallback path to PIP2.

This is the first step in implementing new UMO experience for
pip, next is creating new PipMenuView for the new redesign.

Flag: com.android.wm.shell.enable_pip_umo_experience
Bug: 307998712
Screenshot: screenshot/8AGeK9E3PwHAgdh.png
Test: See the before and after screenshot
Change-Id: I9782be7bc3d6f9ddbd8610b9078da25e60447aa0