codeintel: Update git object preview to use new graphql resolvers
Created by: efritz
This PR updates the UI to use the new resolvers introduced in https://github.com/sourcegraph/sourcegraph/pull/26107. Instead of ad-hoc pulling from branch and tag endpoints, we have a centralized query that can resolve a code intelligence configuration policy into a set of named branches/tags to power the preview when at the repository level.