PYTHON-4779 Use slots for Selection and TopologyDescription

Author: blink1073

pymongo/server_selectors.py

@@ -32,6 +32,8 @@
 class Selection:
     """Input or output of a server selector function."""
 
+    __slots__ = ("totopology_description", "server_descriptions", "primary", "common_wire_version")
+
     @classmethod
     def from_topology_description(cls, topology_description: TopologyDescription) -> Selection:
         known_servers = topology_description.known_servers

pymongo/topology_description.py

@@ -61,6 +61,16 @@ class _TopologyType(NamedTuple):
 
 
 class TopologyDescription:
+    __slots__ = (
+        "_topology_type",
+        "_replica_set_name",
+        "_server_descriptions",
+        "_max_set_version",
+        "_max_election_id",
+        "_incompatible_err",
+        "_ls_timeout_minutes",
+    )
+
     def __init__(
         self,
         topology_type: int,