cloud: enable prometheus server

This makes cloud components start a Prometheus server on a separate port
(:4243 by default) using either gRPC TLS credentials or plain HTTP.

The Prometheus server currently only export the standard Go/Process
metrics that the default Prometheus library exports.

Change-Id: I9f2ae20c34446c0e10a946d4a93251764f5d2fce
Reviewed-on: https://review.monogon.dev/c/monogon/+/1599
Reviewed-by: Leopold Schabel <leo@monogon.tech>
Tested-by: Jenkins CI
diff --git a/cloud/lib/component/BUILD.bazel b/cloud/lib/component/BUILD.bazel
index d705997..dcbe0fe 100644
--- a/cloud/lib/component/BUILD.bazel
+++ b/cloud/lib/component/BUILD.bazel
@@ -18,6 +18,9 @@
         "@com_github_golang_migrate_migrate_v4//database/cockroachdb",
         "@com_github_golang_migrate_migrate_v4//source",
         "@com_github_lib_pq//:pq",
+        "@com_github_prometheus_client_golang//prometheus",
+        "@com_github_prometheus_client_golang//prometheus/collectors",
+        "@com_github_prometheus_client_golang//prometheus/promhttp",
         "@io_k8s_klog_v2//:klog",
         "@org_golang_google_grpc//:go_default_library",
         "@org_golang_google_grpc//credentials",