DDS metadata: add ToA, backend, actual FPS, raw-frame-size

[maloel]

• adds dds_sample definition in dds-defines.h
• adds another variant of time_to_double
• add dds_sample to stream on_data_available callbacks
• add optional fallback parser to md_array_parser
• add the "missing" metadata to all software sensors (not just DDS sensors)
• fix DDS frame creation to add missing fields

NOTE:

• this means that software frames will have an 'actual_fps' now, whereas before they did not
• the syncer uses actual-fps
• the syncer tests failed, so I made them manually set the actual fps to 0, thereby forcing it to "not be available"
• this can be considered a change of behavior, though I know of no use of actual-fps outside of the syncer, and IMO the new behavior is desired (as it is with DDS) if the SW parameters are set correctly

Tracked on [RSDEV-1937]

[OhadMeir]

• this can be considered a change of behavior, though I know of no use of actual-fps outside of the syncer, and IMO the new behavior is desired (as it is with DDS) if the SW parameters are set correctly

I agree that this is a desired behavior. If some user/use-case needs the old behavior he can set it to 0.