New P4RuntimeClient implementation that supports batching and error reporting

The new client API supports batching and provides detailed response for
write requests (e.g. if entity already exists when inserting), which was
not possible with the old one.

This patch includes:
- New more efficient implementation of P4RuntimeClient (no more locking,
use native gRPC executor, use stub deadlines)
- Ported all codecs to new AbstractCodec-based implementation (needed to
implement codec cache in the future)
- Uses batching in P4RuntimeFlowRuleProgrammable and
P4RuntimeGroupActionProgrammable
- Minor changes to PI framework runtime classes

Change-Id: I3fac42057bb4e1389d761006a32600c786598683
diff --git a/protocols/p4runtime/ctl/src/main/java/org/onosproject/p4runtime/ctl/controller/ChannelEvent.java b/protocols/p4runtime/ctl/src/main/java/org/onosproject/p4runtime/ctl/controller/ChannelEvent.java
new file mode 100644
index 0000000..0a77e46
--- /dev/null
+++ b/protocols/p4runtime/ctl/src/main/java/org/onosproject/p4runtime/ctl/controller/ChannelEvent.java
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2019-present Open Networking Foundation
+ *
+ * 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 org.onosproject.p4runtime.ctl.controller;
+
+import org.onosproject.net.DeviceId;
+import org.onosproject.p4runtime.api.P4RuntimeEventSubject;
+
+/**
+ * Channel event in P4Runtime.
+ */
+public final class ChannelEvent implements P4RuntimeEventSubject {
+
+    public enum Type {
+        OPEN,
+        CLOSED,
+        ERROR
+    }
+
+    private DeviceId deviceId;
+    private Type type;
+
+    /**
+     * Creates channel event with given status and throwable.
+     *
+     * @param deviceId  the device
+     * @param type      error type
+     */
+    public ChannelEvent(DeviceId deviceId, Type type) {
+        this.deviceId = deviceId;
+        this.type = type;
+    }
+
+    /**
+     * Gets the type of this event.
+     *
+     * @return the error type
+     */
+    public Type type() {
+        return type;
+    }
+
+    @Override
+    public DeviceId deviceId() {
+        return deviceId;
+    }
+}