authz: make SubRepoPermissionChecker only have Permissions
Created by: bobheadxi
Follow-up to https://github.com/sourcegraph/sourcegraph/pull/27054, pulled from https://github.com/sourcegraph/sourcegraph/pull/27012
Created by: bobheadxi
Follow-up to https://github.com/sourcegraph/sourcegraph/pull/27054, pulled from https://github.com/sourcegraph/sourcegraph/pull/27012