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/BUILD.bazel b/metropolis/node/kubernetes/BUILD.bazel
index 530723f..3245964 100644
--- a/metropolis/node/kubernetes/BUILD.bazel
+++ b/metropolis/node/kubernetes/BUILD.bazel
@@ -21,7 +21,6 @@
         "//go/logging",
         "//go/net/tinylb",
         "//metropolis/node",
-        "//metropolis/node/core/clusternet",
         "//metropolis/node/core/consensus",
         "//metropolis/node/core/curator/proto/api",
         "//metropolis/node/core/curator/watcher",
@@ -29,6 +28,7 @@
         "//metropolis/node/core/localstorage",
         "//metropolis/node/core/metrics",
         "//metropolis/node/core/network",
+        "//metropolis/node/core/network/ipam",
         "//metropolis/node/kubernetes/authproxy",
         "//metropolis/node/kubernetes/clusternet",
         "//metropolis/node/kubernetes/metricsprovider",