Make facecam work in PIP

[cslaviero]

Hi, I was wondering if facecam could work in PiP mode while Blink is in background. My usecase (not exclusive) would be that of a professor using Blink to teach programming and computer science stuff, and moving back and forth from drawing in some whiteboard app to Blink. iPadOS16 has enabled developers to keep the webcam enabled while in background (or so) : https://developer.apple.com/documentation/avfoundation/capture_setup/accessing_the_camera_while_multitasking .

[yury]

I did initial prototype - looks promising.
Tracking issue #1665