Camera2: Factor out Camera2Client::Parameters

Move the parameter structure and the various utility methods using it
to its own class. Rename LockedParameters to SharedParameters to match
the Mutex naming convention.

Also move CameraMetadata to camera2 directory for organization.

No functional changes.

Bug: 6243944
Change-Id: Ie60b535936ecfda9bf23361d52604abf515c83d0