Camera: Clarify multi-camera RAW and FOV behaviors

- RAW capability can exist for multi-camera even if physical cameras are
of different sizes/capabilities.
- FOV for all processes streams must be the same regardless of logical
or physical streams.

Test: Build and read docs
Bug: 118906351
Bug: 126220135
Change-Id: I14ab4844630a048e66a42ec3a776c87830565e49