camera: Support multiple physical camera requests

Capture requests could include settings for different physical
cameras. Camera service should always check whether such
extended requests refer to valid physical devices and process
them accordingly.
Fix some stability issues in the camera native tests.

Test: Basic camera sanity using camera application,
camera_client_test, Camera CTS
Bug: 64691172

Change-Id: I68b81e983dd0b7caebfa03e4f0cf283f2a91dc7a