Camera: Add support for dynamic physical camera switch

- Add activePhysicalId metadata tag for logical camera to indicate current
active physical camera backing logical camera.
- Clarify synchronization between optical and digital zoom controls.
- Specify metadata tags behaviors when active physical camera switches.

Test: Camera CTS for Pixel 3 logical camera
Bug: 77915333
Change-Id: I0cdb523587e8eef324cb1043914c774824d71159