make DB helper functions free functions

Also changes the drop function so that it can drop multiple tables
at once.

src/nominatim_db/tools/replication.py

@@ -20,7 +20,7 @@ import requests
 
 from ..errors import UsageError
 from ..db import status
-from ..db.connection import Connection, connect
+from ..db.connection import Connection, connect, server_version_tuple
 from .exec_utils import run_osm2pgsql
 
 try:
@@ -155,7 +155,7 @@ def run_osm2pgsql_updates(conn: Connection, options: MutableMapping[str, Any]) -
 
     # Consume updates with osm2pgsql.
     options['append'] = True
-    options['disable_jit'] = conn.server_version_tuple() >= (11, 0)
+    options['disable_jit'] = server_version_tuple(conn) >= (11, 0)
     run_osm2pgsql(options)
 
     # Handle deletions