refactor: split reenterable_schema_change_request
Summary
- refactor: split reenterable_schema_change_request
Previously function was ~700 loc. The patch splits out the logic of conversion from ir node to operation. Previously there were two stages, initial validation that constructed intermediate structure and then intermediate structure was transformed into Op potentially several times in case of retries. The patch removes intermediate conversion by direct mapping from ir node to op. It makes reading more convenient since there is no need to jump back and forth between initial checks and actual Op construction. Another benefit is that some checks need to be repeated on each retry since retries originate from conflicts and conflicts change system state. So in newer state operation may no longer make sense. By coupling both operations together there is no way a check can be missed in the retry phase.
We still do some cloning here and there. We can probably improve on that by constructing Op once and then adjusting it in place for conslicts but since retries should be rare in practice it shouldnt be a problem.
Additionally we do a lot of conversion between SmolStr and String. We need to use SmolStr in more placese inside picodata so we dont need to do that.
- Cherry-pick to: none
- Docs follow-up: not necessary