Delete TRSNCEIVER tables while config reload (#3726)

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#### What I did
Removed TRANSCEIVER tables while config reload / load minigraph is executed.
This code adds the option to reserve TRANSCEIVER_INFO table if xcvrd is being restarted. - https://github.com/sonic-net/sonic-platform-daemons/blob/0cb36447ebfda390d999df6516beac4c17315a7b/sonic-xcvrd/xcvrd/xcvrd.py#L2199

The fix introduced here comes to fix the issue that the table remains also after config reload / load minigraph, which may cause config DB and TRANSCEIVER_INFO table have different ports keys.

#### How I did it
Update config reload command to delete TRANSCEIVER tables: ["TRANSCEIVER_INFO", "TRANSCEIVER_STATUS", "TRANSCEIVER_PM", "TRANSCEIVER_FIRMWARE_INFO", "TRANSCEIVER_DOM_SENSOR", "TRANSCEIVER_DOM_THRESHOLD"]
#### How to verify it
Execute config reload and make sure TRANSCEIVER tables are deleted

#### Previous command output (if the output of a command-line utility has changed)

#### New command output (if the output of a command-line utility has changed)

config/main.py

@@ -1323,6 +1323,18 @@ def flush_configdb(namespace=DEFAULT_NAMESPACE):
     return client, config_db
 
 
+def delete_transceiver_tables():
+    tables = ["TRANSCEIVER_INFO", "TRANSCEIVER_STATUS", "TRANSCEIVER_PM",
+              "TRANSCEIVER_FIRMWARE_INFO", "TRANSCEIVER_DOM_SENSOR", "TRANSCEIVER_DOM_THRESHOLD"]
+    state_db_del_pattern = "|*"
+
+    # delete TRANSCEIVER tables from State DB
+    state_db = SonicV2Connector(use_unix_socket_path=True)
+    state_db.connect(state_db.STATE_DB, False)
+    for table in tables:
+        state_db.delete_all_by_pattern(state_db.STATE_DB, table + state_db_del_pattern)
+
+
 def migrate_db_to_lastest(namespace=DEFAULT_NAMESPACE):
     # Migrate DB contents to latest version
     db_migrator = '/usr/local/bin/db_migrator.py'
@@ -1902,6 +1914,7 @@ def reload(db, filename, yes, load_sysinfo, no_service_restart, force, file_form
                 cfg_hwsku = output.strip()
 
             client, config_db = flush_configdb(namespace)
+            delete_transceiver_tables()
 
             if load_sysinfo:
                 if namespace is DEFAULT_NAMESPACE:
@@ -2037,6 +2050,7 @@ def load_minigraph(db, no_service_restart, traffic_shift_away, override_config,
     #Stop services before config push
     if not no_service_restart:
         log.log_notice("'load_minigraph' stopping services...")
+        delete_transceiver_tables()
         _stop_services()
 
     # For Single Asic platform the namespace list has the empty string