* Abstract SteadyClockCore to follow Nintendo changes in 4.x
This is the ground work for 4.0.0 support
* Implement TickBasedSteadyClockCore
Preparation for the ephemeral clock.
* Refactor SystemClockCore to follow 4.0.0 changes
* Implement EphemeralNetworkSystemClock
* Implement GetSnapshotClock & GetSnapshotClockFromSystemClockContext
* Implement CalculateStandardUserSystemClockDifferenceByUser & CalculateSpanBetween
* Remove an outdated comment & unused import
* Fix a nit and GetClockSnapshot
* Address comment
