tidy-up: miscellaneous

- badwords: replace stray synonyms with 'null-terminator'.
- tests/FILEFORMAT.md: tidy up feature descriptions.
- printf: replace stray `%i` masks with `%d` for consistency.
- pytest: add comments for empty excepts to try silencing GitHub CodeQL
  warnings.
- tool1394, unit1675: merge nested `if`s.
- dnscache: fix typo in comment.
- fix whitespace, indent and newlines.

Closes #21921

tests/http/testenv/ws_echo_server.py

@@ -37,6 +37,7 @@ async def echo(websocket):
         async for message in websocket:
             await websocket.send(message)
     except ConnectionClosedError:
+        # websocket connection closed by client
         pass