Add image verifier transfer service plugin system based on a binary directory

Signed-off-by: Ethan Lowman <ethan.lowman@datadoghq.com>

pkg/imageverifier/bindir/testdata/verifiers/slow_child_process.go

@@ -0,0 +1,40 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License 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.
+*/
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+)
+
+func main() {
+	// Launch a slow child process by re-executing this binary with the -sleep-forever flag.
+	if len(os.Args) == 2 && os.Args[1] == "-sleep-forever" {
+		fmt.Println("sleeping forever...")
+		for {
+		}
+	}
+
+	thisBin := os.Args[0]
+	cmd := exec.Command(thisBin, "-sleep-forever")
+	b, err := cmd.CombinedOutput()
+	fmt.Println(string(b))
+	if err != nil {
+		panic(err)
+	}
+}