Expand visibility of projection state API so Android Auto can access it.

The PROJECTION_TYPE_* constants and re{quest,lease}Projection APIs were originally marked @TestApi and @hide, but Android Auto needs them to be part of the @SystemApi to be able to use them.

Bug: 134997071
Bug: 169702986
Test: Unit tests, tested against Android Auto
Change-Id: Id8f3fb8697726ba20ea5a2843026c2083c0bec92