Make OfflineNodeEntity Probe non-IpmiFru

Since OfflineNodeEntityInfo is constant for a machine, this can match multiple RawFru objects depending on how the ProbeV2 logic is structured today. To avoid the edge cases introduced by combining OfflineNodeEntity probe and IpmiFru probe conditional logic, make OfflineNodeEntity probe behave like a keyword probe like `TRUE`.

For today's use case, OfflineNodeEntity probe logic does not need to be combined with any physical RawFru fields. When a OfflineNodeEntity probe is encountered, create a new object in the FruTable for it. Only one such fru is created per config and they must have unique names.

#tlbmc

PiperOrigin-RevId: 842416137
Change-Id: Ife11cf80e94705d8f6675db19e8dfa1f360bcb08