search: make job creation not depend on resolver
Created by: rvantonder
Redo of https://github.com/sourcegraph/sourcegraph/pull/31129, GH autoclosed after I accidentally pushed empty branch.
Stacked on https://github.com/sourcegraph/sourcegraph/pull/31128.
As in title. Will move this out of graphqlbackend
next
Test plan
Semantics-preserving, covered by tests