Add an API to allow for creating private virtual displays.

This change enables applications to create a private virtual
display that renders its content to a surface of its own creation.
The display is private in the sense that only the application
that owns the display is allowed to place windows upon it.
Mirroring and blanking is also disabled for these displays.

Bug: 9192512
Change-Id: I852ea07f0c7df1d244e354e3daca3a6960285ca0