[FlexCounter] Add trap flow counter support (#954)

* [FlexCounter] Add trap flow counter support
* Flow counters are usually used for debugging, troubleshooting and performance enhancement processes. Host interface trap counter can get number of received traps per Trap ID.

Author: Junchao-Mellanox

meta/SaiSerialize.cpp

@@ -1007,6 +1007,14 @@ std::string sai_serialize_tunnel_stat(
     return sai_serialize_enum(counter, &sai_metadata_enum_sai_tunnel_stat_t);
 }
 
+std::string sai_serialize_counter_stat(
+        _In_ const sai_counter_stat_t counter)
+{
+    SWSS_LOG_ENTER();
+
+    return sai_serialize_enum(counter, &sai_metadata_enum_sai_counter_stat_t);
+}
+
 std::string sai_serialize_queue_attr(
         _In_ const sai_queue_attr_t attr)
 {

meta/sai_serialize.h

@@ -122,6 +122,9 @@ std::string sai_serialize_buffer_pool_stat(
 std::string sai_serialize_tunnel_stat(
         _In_ const sai_tunnel_stat_t counter);
 
+std::string sai_serialize_counter_stat(
+        _In_ const sai_counter_stat_t counter);
+
 std::string sai_serialize_queue_attr(
         _In_ const sai_queue_attr_t attr);