CameraService: Remove device HALv2 support, other cleanup

HALv2 only ever shipped with Nexus 10, and has been fully superceded by
HALv3. Remove it to allow for various code simplifications and cleanup.

- Remove Camera2Device
- Remove various special-case codepaths for supporting Camera2Device
- Remove CameraDeviceFactory, since it only creates Camera3Devices now
- Remove BurstCapture and associated CaptureSequence/Parameters code
- Remove old ZslProcessor and simplify ZslProcessor hierarchy to be
  just ZslProcessor3, which is renamed to just ZslProcessor
- Add service-init-time check for unsupported device versions
- Fix assorted compiler warnings, some old, some new
- Remove references to HALv2 when possible

Bug: 25866588
Change-Id: Ia1063264d315f9b742ec5cdd0483539310894f5e