feat: implement optional count for postgresql provider

This work has been done to allow the result count to be enabled or disabled for the PostgreSQL provider. By disabling the count you can get improved performance on large datasets but on smaller datasets this is unlikely to have any affect.

Author: mdearos

tests/provider/test_postgresql_provider.py

@@ -85,7 +85,8 @@ def config():
         },
         'id_field': 'osm_id',
         'table': 'hotosm_bdi_waterways',
-        'geom_field': 'foo_geom'
+        'geom_field': 'foo_geom',
+        'count': 'true'
     }