m/node: move clusternet under network

Move the clusternet network side under the core/network umbrella and
rename it to overlay. Also split out types.go into the ipam package
to get the overlay package out of a lot of dependents which only import
it for the Prefixes type which should be part of the ipam package.

This is a clean move with no functional changes intended yet, these
will be stacked on top.

Change-Id: I6a6a6964af9d608f9ec3bf75b386c010cfff1df4
Reviewed-on: https://review.monogon.dev/c/monogon/+/4500
Tested-by: Jenkins CI
Reviewed-by: Jan Schär <jan@monogon.tech>
diff --git a/metropolis/node/kubernetes/clusternet/BUILD.bazel b/metropolis/node/kubernetes/clusternet/BUILD.bazel
index 79bedbe..839d946 100644
--- a/metropolis/node/kubernetes/clusternet/BUILD.bazel
+++ b/metropolis/node/kubernetes/clusternet/BUILD.bazel
@@ -7,7 +7,7 @@
     visibility = ["//metropolis/node/kubernetes:__subpackages__"],
     deps = [
         "//go/logging",
-        "//metropolis/node/core/clusternet",
+        "//metropolis/node/core/network/ipam",
         "//osbase/event",
         "//osbase/supervisor",
         "@io_k8s_api//core/v1:core",