Some observers assume that they will observe all the segments for a
given stream, and that they will observe those segments in a sequential
stream over one or more iterations.
This change updates the range provider from rangedlooptest to provide
these guarantees.
The change also removes the Mock suffix from the provider/splitter types
since the package name (rangedlooptest) implies that the type is a test
double.
Change-Id: I927c409807e305787abcde57427baac22f663eaa
