Media Projection self content sharing (1/n)

- Add an API in MediaProjectionConfiguration to enable app content
  projection
- Add APIs and underlying services to query app for media projection app
  content

Test: atest MediaProjectionAppContentTest
Bug: 398757866
Flag: com.android.media.projection.flags.app_content_sharing

Change-Id: Ic3abf3f948067ed913a881b1436f2110627de7f5