Search backend: simplify `repo:contains` resolution

Created by: camdencheek

I think I figured out the right way to use Zoekt's Type and List() queries, which simplifies the repo:contains... resolution during repo resolution. This change is also required for correct behavior of the negated form of the predicate (which is in the works).

Stacked on https://github.com/sourcegraph/sourcegraph/pull/40239

Test plan

Integration tests, manual testing, pulled this off another larger change that I've been testing more extensively.