Remove deprecated label access

Using FieldDescriptor.label is [now deprecated][1], with some new
properties to replace these usages.

Unfortunately, the [new types aren't in typeshed yet][2], so we have to
ignore the types until the properties are released upstream.

[1]: protocolbuffers/protobuf@64a76e6
[2]: python/typeshed#14702

Author: stefanvanburen

protovalidate/internal/rules.py

@@ -155,7 +155,7 @@ def _scalar_field_value_to_cel(val: typing.Any, field: descriptor.FieldDescripto
 
 
 def _field_value_to_cel(val: typing.Any, field: descriptor.FieldDescriptor) -> celtypes.Value:
-    if field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
+    if field.is_repeated:  # type: ignore
         if field.message_type is not None and field.message_type.GetOptions().map_entry:
             return _map_field_value_to_cel(val, field)
         return _repeated_field_value_to_cel(val, field)
@@ -165,7 +165,7 @@ def _field_value_to_cel(val: typing.Any, field: descriptor.FieldDescriptor) -> c
 def _is_empty_field(msg: message.Message, field: descriptor.FieldDescriptor) -> bool:
     if field.has_presence:
         return not _proto_message_has_field(msg, field)
-    if field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
+    if field.is_repeated:  # type: ignore
         return len(_proto_message_get_field(msg, field)) == 0
     return _proto_message_get_field(msg, field) == field.default_value
 
@@ -194,7 +194,7 @@ def _map_field_to_cel(msg: message.Message, field: descriptor.FieldDescriptor) -
 
 
 def field_to_cel(msg: message.Message, field: descriptor.FieldDescriptor) -> celtypes.Value:
-    if field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
+    if field.is_repeated:  # type: ignore
         return _repeated_field_to_cel(msg, field)
     elif field.message_type is not None and not _proto_message_has_field(msg, field):
         return None
@@ -484,19 +484,15 @@ def check_field_type(field: descriptor.FieldDescriptor, expected: int, wrapper_n
 
 
 def _is_map(field: descriptor.FieldDescriptor):
-    return (
-        field.label == descriptor.FieldDescriptor.LABEL_REPEATED
-        and field.message_type is not None
-        and field.message_type.GetOptions().map_entry
-    )
+    return field.is_repeated and field.message_type is not None and field.message_type.GetOptions().map_entry  # type: ignore
 
 
 def _is_list(field: descriptor.FieldDescriptor):
-    return field.label == descriptor.FieldDescriptor.LABEL_REPEATED and not _is_map(field)
+    return field.is_repeated and not _is_map(field)  # type: ignore
 
 
 def _zero_value(field: descriptor.FieldDescriptor):
-    if field.message_type is not None and field.label != descriptor.FieldDescriptor.LABEL_REPEATED:
+    if field.message_type is not None and not field.is_repeated:  # type: ignore
         return _field_value_to_cel(message_factory.GetMessageClass(field.message_type)(), field)
     else:
         return _field_value_to_cel(field.default_value, field)
@@ -1003,7 +999,7 @@ def _new_field_rule(
         field: descriptor.FieldDescriptor,
         rules: validate_pb2.FieldRules,
     ) -> FieldRules:
-        if field.label != descriptor.FieldDescriptor.LABEL_REPEATED:
+        if not field.is_repeated:  # type: ignore
             return self._new_scalar_field_rule(field, rules)
         if field.message_type is not None and field.message_type.GetOptions().map_entry:
             key_rules = None
@@ -1057,7 +1053,7 @@ def _new_rules(self, desc: descriptor.Descriptor) -> list[Rules]:
                 if value_field.type != descriptor.FieldDescriptor.TYPE_MESSAGE:
                     continue
                 result.append(MapValMsgRule(self, field, key_field, value_field))
-            elif field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
+            elif field.is_repeated:
                 result.append(RepeatedMsgRule(self, field))
             else:
                 result.append(SubMsgRule(self, field))