More robust P4Runtime group handling

This patch solves the PENDING_UPDATE and PENDING_ADD_RETRY issue
observed on the ONS EU topology.

The P4Runtime action profile group handling has been re-implemented to
be robust against inconsistencies of the device mirror, which is now
periodically synchronized with the device state. Similarly, we implement
a routine in the P4RuntimeClient to cleanup unused action profile
members.

This patch includes also:
-  Refactor PI handle classes to allow creating handles without the
entity instance
- Use list instead of collections in P4RuntimeClient methods, as order
of updates sent and/or entities received from the device is important

Change-Id: I2e7964ce90f43d66680131b47ab52aca32ab55d2
diff --git a/core/api/src/main/java/org/onosproject/net/pi/runtime/PiTableEntry.java b/core/api/src/main/java/org/onosproject/net/pi/runtime/PiTableEntry.java
index 04b2528..f8a1460 100644
--- a/core/api/src/main/java/org/onosproject/net/pi/runtime/PiTableEntry.java
+++ b/core/api/src/main/java/org/onosproject/net/pi/runtime/PiTableEntry.java
@@ -135,6 +135,7 @@
         }
         PiTableEntry that = (PiTableEntry) o;
         return priority == that.priority &&
+                cookie == that.cookie &&
                 Double.compare(that.timeout, timeout) == 0 &&
                 Objects.equal(tableId, that.tableId) &&
                 Objects.equal(matchKey, that.matchKey) &&
@@ -145,7 +146,7 @@
     @Override
     public int hashCode() {
         return Objects.hashCode(tableId, matchKey, isDefaultAction, tableAction,
-                                priority, timeout);
+                                priority, cookie, timeout);
     }
 
     @Override