Move dynamic plugins to a subpackage

Signed-off-by: Derek McGowan <derek@mcg.dev>

plugin/dynamic/dynamic.go

@@ -0,0 +1,37 @@
+/*
+   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 dynamic
+
+import "fmt"
+
+// Load loads all plugins at the provided path into containerd.
+//
+// Load is currently only implemented on non-static, non-gccgo builds for amd64
+// and arm64, and plugins must be built with the exact same version of Go as
+// containerd itself.
+func Load(path string) (err error) {
+	defer func() {
+		if v := recover(); v != nil {
+			rerr, ok := v.(error)
+			if !ok {
+				rerr = fmt.Errorf("%s", v)
+			}
+			err = rerr
+		}
+	}()
+	return loadPlugins(path)
+}