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

docs/internals/DYNBUF.md

@@ -9,7 +9,7 @@ SPDX-License-Identifier: curl
 This is the internal module for creating and handling "dynamic buffers". This
 means buffers that can be appended to, dynamically and grow to adapt.
 
-There is always a terminating zero put at the end of the dynamic buffer.
+There is always a null-terminator put at the end of the dynamic buffer.
 
 The `struct dynbuf` is used to hold data for each instance of a dynamic
 buffer. The members of that struct **MUST NOT** be accessed or modified
@@ -120,8 +120,8 @@ trusted or used anymore after the next buffer manipulation call.
 size_t curlx_dyn_len(const struct dynbuf *s);
 ```
 
-Returns the length of the buffer in bytes. Does not include the terminating
-zero byte.
+Returns the length of the buffer in bytes. Does not include the
+null-terminator byte.
 
 ## `curlx_dyn_setlen`