Introduce SystemAPI MediaProjectionGlobal

This API can be used from calls outside applications to create a virtual
display for mirroring. The permission checks in system server are still
in place so the caller must have CAPTURE_VIDEO_OUTPUT permission. This
class is intented to be used by systems that to stream device content,
but not from an application. In most cases, this will be called from
Shell or a system application.

Test: MediaProjectGlobalTest
Bug: 237664947
Change-Id: I43f79c83db7c82c0b682ef174fb1a5ab83795489