go/net/psample: init

This adds a minimal golang implementation facilitating network packet
sampling based on 'psample' kernel module.

Metropolis kernel configuration was modified both in order for this
change to be testable in a ktest, as well as to make sure Metropolis
will be able to run the included code.

Change-Id: Ie6a4721455f26644b6be01aa6190cf87f21355f3
Reviewed-on: https://review.monogon.dev/c/monogon/+/1102
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/test/ktest/init/BUILD.bazel b/metropolis/test/ktest/init/BUILD.bazel
index f6b540f..e48bcb2 100644
--- a/metropolis/test/ktest/init/BUILD.bazel
+++ b/metropolis/test/ktest/init/BUILD.bazel
@@ -12,5 +12,8 @@
     name = "init",
     embed = [":init_lib"],
     pure = "on",
-    visibility = ["//metropolis:__subpackages__"],
+    visibility = [
+        "//go/net/psample:__pkg__",
+        "//metropolis:__subpackages__",
+    ],
 )