Refactor to ensure we call check_consistency (#9470)

The idea here is to stop people forgetting to call `check_consistency`. Folks can still just pass in `None` to the new args in `build_sequence_generator`, but hopefully they won't.

synapse/storage/util/sequence.py

@@ -251,9 +251,14 @@ class LocalSequenceGenerator(SequenceGenerator):
 
 
 def build_sequence_generator(
+    db_conn: "LoggingDatabaseConnection",
     database_engine: BaseDatabaseEngine,
     get_first_callback: GetFirstCallbackType,
     sequence_name: str,
+    table: Optional[str],
+    id_column: Optional[str],
+    stream_name: Optional[str] = None,
+    positive: bool = True,
 ) -> SequenceGenerator:
     """Get the best impl of SequenceGenerator available
 
@@ -265,8 +270,23 @@ def build_sequence_generator(
         get_first_callback: a callback which gets the next sequence ID. Used if
             we're on sqlite.
         sequence_name: the name of a postgres sequence to use.
+        table, id_column, stream_name, positive: If set then `check_consistency`
+            is called on the created sequence. See docstring for
+            `check_consistency` details.
     """
     if isinstance(database_engine, PostgresEngine):
-        return PostgresSequenceGenerator(sequence_name)
+        seq = PostgresSequenceGenerator(sequence_name)  # type: SequenceGenerator
     else:
-        return LocalSequenceGenerator(get_first_callback)
+        seq = LocalSequenceGenerator(get_first_callback)
+
+    if table:
+        assert id_column
+        seq.check_consistency(
+            db_conn=db_conn,
+            table=table,
+            id_column=id_column,
+            stream_name=stream_name,
+            positive=positive,
+        )
+
+    return seq