Add CameraCharacteristics in VirtualCameraConfig

Add support for CameraCharacteristics for virtual cameras, starting with
the VirtualCameraConfig to be passed when the VD owner creates a virtual
camera.

Also, add a boolean config flag to indicate per frame support of camera
metadata by the VD owner.

Add a @SystemApi Builder for CameraCharacteristics to allow VD owner
priviledged apps to create CameraCharacteristics that can be set for VirtualCameras.

Bug: 371167033
Test: atest VirtualCameraConfigTest
Flag: android.companion.virtualdevice.flags.virtual_camera_metadata
Change-Id: I63292838459466abaac68375d4b6c2f4ddced67f