fix: make ddl wait to be committed in pico.sql

fix: make ddl wait to be committed in pico.sql

Before current commit, sql waited for ddl operations to be prepared in the cluster, but not committed or aborted. As a result, when the user queries the space right after the previous ddl successfully returned "ok", it was possible to retrieve "no space found" error.

The MR was produced by https://git.picodata.io/picodata/picodata/pgproto/-/issues/17