osbase/net/dhcp4c: move package out of metropolis

Move the dhcp4c package from metropolis/node/core/network/dhcp4c to
osbase/net/dhcp4c. The package is not specific to metropolis, and is
also used by nanoswitch and cloud/agent.

Change-Id: I508261c93c623d5b7a33a2089da11625b7a3abd0
Reviewed-on: https://review.monogon.dev/c/monogon/+/4565
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/metropolis/test/nanoswitch/BUILD.bazel b/metropolis/test/nanoswitch/BUILD.bazel
index 9aff921..ef80101 100644
--- a/metropolis/test/nanoswitch/BUILD.bazel
+++ b/metropolis/test/nanoswitch/BUILD.bazel
@@ -11,9 +11,9 @@
     visibility = ["//visibility:private"],
     deps = [
         "//metropolis/node",
-        "//metropolis/node/core/network/dhcp4c",
-        "//metropolis/node/core/network/dhcp4c/callback",
         "//osbase/bringup",
+        "//osbase/net/dhcp4c",
+        "//osbase/net/dhcp4c/callback",
         "//osbase/supervisor",
         "//osbase/test/socksproxy",
         "@com_github_google_nftables//:nftables",