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NuGet: changed from MS.Bcl.immutable 1.1.29 to the new name System.Collection.Immutable 1.1.32

- note: only impacts experimental in memory db
Merge branch 'master' into refac_tuples
Subspace refactoring: moved ToRange() to the properties subspace.Keys and subpsace.Tuples

- subspace.Tuples.ToRange() has the same behavior as the old subspace.ToRange() (prefix+\x00 .. prefix+\xFF)
- subspace.Keys.ToRange() includes ALL the keys, and is the equivalent of FdbKeyRange.StartsWith(subspace.Prefix)
- If you had "subspace.ToRange()" before, you should first change it to "subspace.Tuples.ToRange()" to stay compatible, and then decide if you actually needed "subspace.Keys.ToRange()" or not.