closes#1186, or at least works towards it by implementing an actual
Plan for update queries instead of translating everything inline. This
allows for actually using index's, rewriting const expressions, pushing
predicates instead of hardcoding a full scan in the translation.
### TODOs:
1. `RETURNING` clause/result columns
2. `OFFSET` clauses
3. on conflict
### LIMIT:
By supporting `LIMIT` directly in update queries, we'll have to put the
tests outside of the compatibility tests, maybe in the CLI tests.
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#1189