Handle new loop nest constraints during transformation

[jdsteve2]

transformations where loop nest constraints handled:

• [x] split_iname
• [x] remove_unused_inames
• [x] duplicate_inames
• [ ] rename_iname
  • [x] (when new iname doesn't exist)
  • [ ] (when new iname DOES exist)
• [x] (?) tag_inames (currently just erroring if must-nest iname gets tagged as concurrent... anything else need to be done here?
• [ ] join_inames
  • [x] (when within is None)
  • [ ] (when within is not None)
• [ ] map_domain

(in progress of moving in/updating relevant functionality from original PR)