[C#] Port for 85579448575bf9c81138835f34be3c55de137abf  ([Java/cpp]: Added semanticVersion to IR.)
[C#] Port of 3a5390e9590a59f6047b6cc99a9f898c9847bdd3 ([Java]: Fix for handling optionality and null values in enum types by propagating to pseudo super type for encoding.)