[SDFAB-831] Add UPF meters to UpfProgrammable APIs

UPF meters can be of type session or application.
Also, add meter index to sessions and terminations UPF entities.

Change-Id: I8babfca35341a21b234d8eb6edaa2e1c02684210
(cherry picked from commit b25299afaf824a8d352297224e5b9a1285901d00)
diff --git a/core/api/src/main/java/org/onosproject/net/behaviour/upf/UpfEntityType.java b/core/api/src/main/java/org/onosproject/net/behaviour/upf/UpfEntityType.java
index 2e9a26a..c5d5590 100644
--- a/core/api/src/main/java/org/onosproject/net/behaviour/upf/UpfEntityType.java
+++ b/core/api/src/main/java/org/onosproject/net/behaviour/upf/UpfEntityType.java
@@ -30,7 +30,9 @@
     SESSION_UPLINK("session_downlink"),
     TUNNEL_PEER("tunnel_peer"),
     COUNTER("counter"),
-    APPLICATION("application");
+    APPLICATION("application"),
+    SESSION_METER("session_meter"),
+    APPLICATION_METER("application_meter");
 
     private final String humanReadableName;