Camera: Add initial offline camera session implementation

Offline camera sessions allow clients to migrate still
ongoing capture requests to offline processing mode.
When offline mode is enabled, the initial active capture
session along with the open camera device can be closed
and further re-used while offline processing is still
ongoing.
Split and re-use parts of camera device implementation
along with its current state for offline mode.

Bug: 135142453
Test: Camera CTS
Change-Id: I5eb4055e2af4265ece0fb7271bdf5f4cf2d5aaf3