Ops.makeNewFieldTag -> Ops.makeNewTag. Use replicateM_
New field in hole. See full description.

BUG#1: convert happens outside scratch transaction, doesn't get name.

BUG#2: Sugar's holeResult uses show-of-expr to randomize the
guids. Thus every scratch transaction execution gets a different
random-gen, which makes the new field result seem like a different
result each time.

REFACTOR NEEDED: forkScratch to be moved to HoleEdit. holeResult gets
pure expr again