RFC 503: Investigate location resolver caching effect on sub repo filtering

Created by: ryanslade

We perform location caching here: https://github.com/sourcegraph/sourcegraph/blob/d2b68da1f1a194a29287b7d18ad5ad81532d8e2a/enterprise/cmd/frontend/internal/codeintel/resolvers/graphql/resolver.go#L43

We need to confirm how this will behave once we have sub-repo filtering in place. The cache should take into account the user id making the request.