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/test_05_errors.py

@@ -197,6 +197,7 @@ class TestErrors:
                     conn.recv(1)  # wait for ClientHello
                     conn.close()
                 except Exception:
+                    # ignore expected socket error
                     pass
 
             t = threading.Thread(target=accept_and_close)

tests/http/testenv/curl.py

@@ -89,6 +89,7 @@ class RunProfile:
                 'rss': mem.rss,
             })
         except psutil.NoSuchProcess:
+            # process may exit between sampling ticks: ignore this
             pass
 
     def finish(self):
@@ -238,6 +239,7 @@ class RunTcpDump:
                     try:
                         self._proc.wait(timeout=1)
                     except subprocess.TimeoutExpired:
+                        # timeout means tcpdump is still running
                         pass
         except Exception:
             log.exception('Tcpdump')

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