Add logging on startup/shutdown (#8448)

This is so we can tell what is going on when things are taking a while to start up.

The main change here is to ensure that transactions that are created during startup get correctly logged like normal transactions.

synapse/storage/databases/main/schema/delta/56/unique_user_filter_index.py

@@ -1,6 +1,8 @@
 import logging
+from io import StringIO
 
 from synapse.storage.engines import PostgresEngine
+from synapse.storage.prepare_database import execute_statements_from_stream
 
 logger = logging.getLogger(__name__)
 
@@ -46,7 +48,4 @@ def run_create(cur, database_engine, *args, **kwargs):
         select_clause,
     )
 
-    if isinstance(database_engine, PostgresEngine):
-        cur.execute(sql)
-    else:
-        cur.executescript(sql)
+    execute_statements_from_stream(cur, StringIO(sql))