Type hints for tests.appservice (#14990)

* Accept a Sequence of events in synapse.appservice

This avoids some casts/ignores in the tests I'm about to fixup. It seems
that `List[Mock]` is not a subtype of `List[EventBase]`, but
`Sequence[Mock]` is a subtype of `Sequence[EventBase]`. So presumably
`Mock` is considered a subtype of anything, much like `Any`.

* make tests.appservice.test_scheduler pass mypy

* Extra hints in tests.appservice.test_scheduler

* Extra hints in tests.appservice.test_api

* Extra hints in tests.appservice.test_appservice

* Disallow untyped defs

* Changelog

synapse/storage/databases/main/appservice.py

@@ -14,7 +14,17 @@
 # limitations under the License.
 import logging
 import re
-from typing import TYPE_CHECKING, Any, Dict, List, Optional, Pattern, Tuple, cast
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Dict,
+    List,
+    Optional,
+    Pattern,
+    Sequence,
+    Tuple,
+    cast,
+)
 
 from synapse.appservice import (
     ApplicationService,
@@ -257,7 +267,7 @@ class ApplicationServiceTransactionWorkerStore(
     async def create_appservice_txn(
         self,
         service: ApplicationService,
-        events: List[EventBase],
+        events: Sequence[EventBase],
         ephemeral: List[JsonDict],
         to_device_messages: List[JsonDict],
         one_time_keys_count: TransactionOneTimeKeysCount,