integration: simplify CNI-fp and add README.md

* Use delegated plugin call to simplify cni-bridge-cni
* Add README.md for cni-bridge-cni

Signed-off-by: Wei Fu <fuweid89@gmail.com>

integration/failpoint/cmd/containerd-shim-runc-fp-v1/main_linux.go

@@ -0,0 +1,29 @@
+/*
+   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 (
+	"context"
+
+	"github.com/containerd/containerd/runtime/v2/runc/manager"
+	_ "github.com/containerd/containerd/runtime/v2/runc/pause"
+	"github.com/containerd/containerd/runtime/v2/shim"
+)
+
+func main() {
+	shim.RunManager(context.Background(), manager.NewShimManager("io.containerd.runc-fp.v1"))
+}