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/core/api/src/main/java/org/onosproject/net/pi/runtime/PiMulticastGroupEntryHandle.java b/core/api/src/main/java/org/onosproject/net/pi/runtime/PiMulticastGroupEntryHandle.java
index 65a3f28..b74ca8e 100644
--- a/core/api/src/main/java/org/onosproject/net/pi/runtime/PiMulticastGroupEntryHandle.java
+++ b/core/api/src/main/java/org/onosproject/net/pi/runtime/PiMulticastGroupEntryHandle.java
@@ -29,11 +29,11 @@
  * ID.
  */
 @Beta
-public final class PiMulticastGroupEntryHandle extends PiHandle<PiMulticastGroupEntry> {
+public final class PiMulticastGroupEntryHandle extends PiHandle {
 
-    private final long groupId;
+    private final int groupId;
 
-    private PiMulticastGroupEntryHandle(DeviceId deviceId, long groupId) {
+    private PiMulticastGroupEntryHandle(DeviceId deviceId, int groupId) {
         super(deviceId);
         this.groupId = groupId;
     }
@@ -46,7 +46,7 @@
      * @return PI multicast group entry handle
      */
     public static PiMulticastGroupEntryHandle of(DeviceId deviceId,
-                                                 long groupId) {
+                                                 int groupId) {
         return new PiMulticastGroupEntryHandle(deviceId, groupId);
     }
 
@@ -64,6 +64,15 @@
         return new PiMulticastGroupEntryHandle(deviceId, entry.groupId());
     }
 
+    /**
+     * Returns the multicast group ID associated with this handle.
+     *
+     * @return group ID
+     */
+    public int groupId() {
+        return groupId;
+    }
+
     @Override
     public PiEntityType entityType() {
         return PiEntityType.PRE_MULTICAST_GROUP_ENTRY;