Add policy for nearby app streaming

App streaming is when the device starts an app on a virtual display and sends a video stream of the app to nearby devices. The policy specifies options in which app streaming is supported. The default policy is streaming only to devices with the same managed account.

Bug: 179910177
Test: Builds successfully
Change-Id: I1a9424d0de524a0cdfcc00b2bc39196e7f231480