Camera service: Updates in preparation for HIDL

- For all camera2 paths, and anything shared between the legacy API and
  camera2, switch to using strings for camera IDs
- Update ICameraService.addListener to return current set of known
  devices and their status, to allow for immediate return of camera
  devices when first connecting to camera service
- Remove unused code path for getCameraCharacteristics with HALv1
- Add namespace qualifiers to Binder objects that are also used by
  hardware binder.
- Switch to using new HIDL DeviceStatus and TorchStatus enumerations
  for better type safety in the service; map more clearly between
  the HAL, service-internal, and Binder enums.

Test: cts-tradefed run cts -m Camera --skip-connectivity-check -d -o --abi armeabi-v7a --disable-reboot
Bug: 32991422
Change-Id: I765951d9a21000a8432bed9aa0e3604709daa4b1