metropolis/test/launch: add InsecureKey

Currently, the node startup parameters are empty. Let's populate them with a development ('insecure') key when started from the launch library.

Test Plan: Future revision in stack will make use of this.

X-Origin-Diff: phab/D754
GitOrigin-RevId: 0cfa3c1d71911423ff169afc027edb768151de67
diff --git a/metropolis/test/launch/BUILD.bazel b/metropolis/test/launch/BUILD.bazel
index f782fe6..3f9d8fd 100644
--- a/metropolis/test/launch/BUILD.bazel
+++ b/metropolis/test/launch/BUILD.bazel
@@ -2,7 +2,10 @@
 
 go_library(
     name = "go_default_library",
-    srcs = ["launch.go"],
+    srcs = [
+        "insecure_key.go",
+        "launch.go",
+    ],
     importpath = "source.monogon.dev/metropolis/test/launch",
     visibility = ["//metropolis:__subpackages__"],
     deps = [