add metrics config to remote snapshotter rootfs

configure socat to forward requests to inVm metrics server being hosted
by remote snapshotter, and configure remote snapshotter to emit metrics

Signed-off-by: Gavin Inglis <giinglis@amazon.com>

Author: ginglis13

tools/image-builder/files_stargz/etc/containerd-stargz-grpc/config.toml

@@ -0,0 +1,2 @@
+metrics_address = "localhost:8234"
+no_prometheus = false

tools/image-builder/files_stargz/etc/systemd/system/firecracker.target.wants/metrics-socat.service

@@ -0,0 +1 @@
+/etc/systemd/system/metrics-socat.service

tools/image-builder/files_stargz/etc/systemd/system/metrics-socat.service

@@ -0,0 +1,22 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You may
+# not use this file except in compliance with the License. A copy of the
+# License is located at
+#
+#       http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is distributed
+# on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+# express or implied. See the License for the specific language governing
+# permissions and limitations under the License.
+[Unit]
+Description=Metrics Socat
+StartLimitIntervalSec=2
+After=stargz-snapshotter.service
+Requires=stargz-snapshotter.service
+SuccessAction=reboot
+
+[Service]
+Type=simple
+ExecStart=socat VSOCK-LISTEN:10001,reuseaddr,fork TCP:localhost:8234