m/test/e2e/connectivity: add connectivity tester

This adds a connectivity testing framework. It uses pod agents and
communicates with them over stdio. This is used to implement a simple
smoke test and will later be used to test network policy controllers.

Change-Id: If40673a91336dbe3a7a383bf2e9d17736fad3bdc
Reviewed-on: https://review.monogon.dev/c/monogon/+/3756
Reviewed-by: Jan Schär <jan@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/test/e2e/connectivity/spec/gomod-generated-placeholder.go b/metropolis/test/e2e/connectivity/spec/gomod-generated-placeholder.go
new file mode 100644
index 0000000..f09cd57
--- /dev/null
+++ b/metropolis/test/e2e/connectivity/spec/gomod-generated-placeholder.go
@@ -0,0 +1 @@
+package spec