Split DocumentSourceTestOptimizations class and sublasses into QO and QE parts. The subclasses are:

• NotSupported
• RenamesAToB
• RenamesBToC
• RenamesBToA
• NoModifications
• ModificationsUnknown
• RenamesAToB
• RenameCDotDToEPreserveFDotG
• RenameCToDPreserveEFG
• ModifiesAllPaths
• RenameAToXDotYModifyCDotD

I expect in most cases we need QO-only class, but maybe we still need to clean-up some unused methods.

Please create subtasksts if the changes do not fit into one reasonable PR.