[schema.h] Add trap flow counter support (#534)

**What I did**

Add trap flow counter related tables/entries to schema.h. See HLD: sonic-net/SONiC#858

**Why I did it**

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.

**How I verified it**

Manual test/VS test/sonic mgmt test

common/schema.h

@@ -134,6 +134,7 @@ namespace swss {
 #define COUNTERS_PG_INDEX_MAP               "COUNTERS_PG_INDEX_MAP"
 #define COUNTERS_RIF_TYPE_MAP               "COUNTERS_RIF_TYPE_MAP"
 #define COUNTERS_RIF_NAME_MAP               "COUNTERS_RIF_NAME_MAP"
+#define COUNTERS_TRAP_NAME_MAP              "COUNTERS_TRAP_NAME_MAP"
 #define COUNTERS_CRM_TABLE                  "CRM"
 #define COUNTERS_BUFFER_POOL_NAME_MAP       "COUNTERS_BUFFER_POOL_NAME_MAP"
 #define COUNTERS_SWITCH_NAME_MAP            "COUNTERS_SWITCH_NAME_MAP"
@@ -181,6 +182,7 @@ namespace swss {
 #define SWITCH_DEBUG_COUNTER_ID_LIST    "SWITCH_DEBUG_COUNTER_ID_LIST"
 #define MACSEC_SA_ATTR_ID_LIST          "MACSEC_SA_ATTR_ID_LIST"
 #define TUNNEL_ATTR_ID_LIST             "TUNNEL_ATTR_ID_LIST"
+#define FLOW_COUNTER_ID_LIST            "FLOW_COUNTER_ID_LIST"
 #define PLUGIN_TABLE                    "PLUGIN_TABLE"
 #define LUA_PLUGIN_TYPE                 "LUA_PLUGIN_TYPE"
 #define SAI_OBJECT_TYPE                 "SAI_OBJECT_TYPE"
@@ -195,6 +197,7 @@ namespace swss {
 #define PG_PLUGIN_FIELD                     "PG_PLUGIN_LIST"
 #define TUNNEL_PLUGIN_FIELD                 "TUNNEL_PLUGIN_LIST"
 #define BUFFER_POOL_PLUGIN_FIELD            "BUFFER_POOL_PLUGIN_LIST"
+#define FLOW_COUNTER_PLUGIN_FIELD           "FLOW_COUNTER_PLUGIN_FIELD"
 #define FLEX_COUNTER_STATUS_FIELD           "FLEX_COUNTER_STATUS"
 #define FLEX_COUNTER_GROUP_TABLE            "FLEX_COUNTER_GROUP_TABLE"
 #define FLEX_COUNTER_DELAY_STATUS_FIELD     "FLEX_COUNTER_DELAY_STATUS"