[MediaProjection] Do not rely on WindowContext to indicate display

Remove WindowContext for indicating the display to capture;
revert to prior behaviour through VirtualDisplayConfig.
Retrieve the display id to mirror through a pre-existing
DisplayManagerInternal API.

Bug: 272036836
Test: manual screen recording
Test: atest FrameworksServicesTests:DisplayManagerServiceTest
Change-Id: Iecdc175dc4292507fe8ec54c4550c3f8b5620054