Camera2: Immutable metadata

Make all camera metadata immutable once created; requests are
created using CameraRequest.Builder.

- Separate CameraMetadata implementation from interface
- Implement deep copying of metadata
- Requests/results/properties have-a native implementation

Bug: 10360518
Change-Id: Ia6300c237219d39f70c63156fa9ca666d951a36e
20 files changed