[subnet_decap] Introduce subnet decap tables (#861)

Introduce the following four tables for the subnet decap feature:

- tunnel decap term table in APPL_DB
- subnet decap table in CONFIG_DB
- tunnel table in STATE_DB
- tunnel decap term table in STATE_DB

Signed-off-by: Longxiang Lyu <lolv@microsoft.com>

common/schema.h

@@ -39,6 +39,7 @@ namespace swss {
 #define APP_ROUTE_TABLE_NAME              "ROUTE_TABLE"
 #define APP_LABEL_ROUTE_TABLE_NAME        "LABEL_ROUTE_TABLE"
 #define APP_TUNNEL_DECAP_TABLE_NAME       "TUNNEL_DECAP_TABLE"
+#define APP_TUNNEL_DECAP_TERM_TABLE_NAME  "TUNNEL_DECAP_TERM_TABLE"
 #define APP_TUNNEL_ROUTE_TABLE_NAME       "TUNNEL_ROUTE_TABLE"
 #define APP_FDB_TABLE_NAME                "FDB_TABLE"
 #define APP_PFC_WD_TABLE_NAME             "PFC_WD_TABLE"
@@ -424,6 +425,7 @@ namespace swss {
 #define CFG_PEER_SWITCH_TABLE_NAME                  "PEER_SWITCH"
 
 #define CFG_TUNNEL_TABLE_NAME                       "TUNNEL"
+#define CFG_SUBNET_DECAP_TABLE_NAME                 "SUBNET_DECAP"
 
 #define CFG_SYSTEM_PORT_TABLE_NAME                  "SYSTEM_PORT"
 #define CFG_VOQ_INBAND_INTERFACE_TABLE_NAME         "VOQ_INBAND_INTERFACE"
@@ -512,6 +514,9 @@ namespace swss {
 #define STATE_BUFFER_PROFILE_TABLE_NAME             "BUFFER_PROFILE_TABLE"
 #define STATE_DHCPv6_COUNTER_TABLE_NAME             "DHCPv6_COUNTER_TABLE"
 
+#define STATE_TUNNEL_DECAP_TABLE_NAME               "TUNNEL_DECAP_TABLE"
+#define STATE_TUNNEL_DECAP_TERM_TABLE_NAME          "TUNNEL_DECAP_TERM_TABLE"
+
 #define STATE_BFD_SESSION_TABLE_NAME                "BFD_SESSION_TABLE"
 #define STATE_ROUTE_TABLE_NAME                      "ROUTE_TABLE"
 #define STATE_VNET_RT_TUNNEL_TABLE_NAME             "VNET_ROUTE_TUNNEL_TABLE"