workspace: introduce bazel downloader config and replace bazeldnf mirror

This rather small change does rework the way we cache our dependencies
by instructing bazel to fetch everything through a custom proxy. See
//build/mirror_proxy:README.me for more infos.

Closes monogon-dev/monogon#178

Change-Id: Ic671fc8233a1cbf37427bbc96339ea8108310e21
Reviewed-on: https://review.monogon.dev/c/monogon/+/3686
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/build/bazel/go.MODULE.bazel b/build/bazel/go.MODULE.bazel
index 19b2bfb..de8ad0d 100644
--- a/build/bazel/go.MODULE.bazel
+++ b/build/bazel/go.MODULE.bazel
@@ -88,7 +88,7 @@
     "io_k8s_kubernetes",
     "io_k8s_pod_security_admission",
     "io_k8s_utils",
-    "net_starlark_go",
+    "org_golang_google_api",
     "org_golang_google_genproto_googleapis_api",
     "org_golang_google_grpc",
     "org_golang_google_protobuf",