Move containerRoot to utils package

Move the containerRoot type to a utils package so that this can be
shared between hooks.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

cmd/nvidia-cdi-hook/utils/container-root.go

@@ -0,0 +1,46 @@
+/**
+# Copyright (c) 2025, NVIDIA CORPORATION.  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.
+# 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 utils
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/moby/sys/symlink"
+)
+
+// A ContainerRoot represents the root filesystem of a container.
+type ContainerRoot string
+
+// HasPath checks whether the specified path exists in the root.
+func (r ContainerRoot) HasPath(path string) bool {
+	resolved, err := r.Resolve(path)
+	if err != nil {
+		return false
+	}
+	if _, err := os.Stat(resolved); err != nil && os.IsNotExist(err) {
+		return false
+	}
+	return true
+}
+
+// Resolve returns the absolute path including root path.
+// Symlinks are resolved, but are guaranteed to resolve in the root.
+func (r ContainerRoot) Resolve(path string) (string, error) {
+	absolute := filepath.Clean(filepath.Join(string(r), path))
+	return symlink.FollowSymlinkInScope(absolute, string(r))
+}