Add interleaved groups available after interleave analysis is done.
See updated tests.
Sure, it would update many tests, but that would be better I suppose to see what happens.
With the -debug flag it was printing out the interleaved groups as well, which I felt takes away focus from the main check lines.
Would it be better to have InterleaveGroup::print(raw_ostream &OS) take care of dumping its members, possibly along with their indices, designated InsertPos, and IG's Factor/Reverse/Alignment attributes?