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

lib/vssh/libssh2.c

@@ -713,7 +713,7 @@ static CURLcode ssh_force_knownhost_key_type(struct Curl_easy *data,
         failf(data, "Found host key type RSA1 which is not supported");
         return CURLE_SSH;
       default:
-        failf(data, "Unknown host key type: %i",
+        failf(data, "Unknown host key type: %d",
               (store->typemask & LIBSSH2_KNOWNHOST_KEY_MASK));
         return CURLE_SSH;
       }