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

scripts/badwords.txt

@@ -29,6 +29,7 @@ nul terminated:null-terminated
 null terminated:null-terminated
 NULL-terminated=null-terminated
 zero terminated:null-terminated
+zero-terminated:null-terminated
 nul terminator:null-terminator
 null terminator:null-terminator
 zero terminator:null-terminator