launch-multi2: split up logs from nodes into prefixed lines

Currently it's impossible to tell apart logs from each node.

In general, we should move this over the the debug logging API instead
of relying on qemu stdout, but this will do for now.

Test Plan: Shouldn't affect any tests, as we don't actually test multi-node setups. Truth be told, we should.

X-Origin-Diff: phab/D670
GitOrigin-RevId: 7b4e170e634096bc40432fbef0844d9924957182
diff --git a/metropolis/test/launch/cli/launch-multi2/BUILD.bazel b/metropolis/test/launch/cli/launch-multi2/BUILD.bazel
index 9f27860..6507ae4 100644
--- a/metropolis/test/launch/cli/launch-multi2/BUILD.bazel
+++ b/metropolis/test/launch/cli/launch-multi2/BUILD.bazel
@@ -7,6 +7,7 @@
     visibility = ["//visibility:private"],
     deps = [
         "//metropolis/node:go_default_library",
+        "//metropolis/node/common/logbuffer:go_default_library",
         "//metropolis/proto/api:go_default_library",
         "//metropolis/test/launch:go_default_library",
         "@com_github_grpc_ecosystem_go_grpc_middleware//retry:go_default_library",