tests: avoid more hard-coded CRLFs in protocol sections

- fix regex to not catch CR (from CRLF), in `PORT`, `EPRT`
  commands, allowing to use `crlf="yes"` more.
- add `crlf="headers"` mode for `protocol` sections.
  To call `subnewlines()` without its force option.
  This is the mode used in `data` sections when `crlf="yes"`.
  (This confusion may be subject to a future commit.)
- subnewlines: apply CRLF to `HEAD` and `CONNECT` HTTP requests.
- subnewlines: apply CRLF to RTSP requests.
- delete remaining empty `protocol` sections.

Reducing the number of `tests/data/test*`:
- CRLF newlines from 11325 to 10295. (119984 lines total)
- files with mixed newlines from 707 to 656. (1890 files total)

Follow-up to 4d2a05d3fe #19284

Closes #19318

docs/tests/FILEFORMAT.md

@@ -663,7 +663,7 @@ command exists with a non-zero status code, the test is considered failed.
 A list of directory entries that are checked for after the test has completed
 and that must not exist. A listed entry existing causes the test to fail.
 
-### `<protocol [nonewline="yes"][crlf="yes"]>`
+### `<protocol [nonewline="yes"][crlf="yes|headers"]>`
 
 the protocol dump curl should transmit, if `nonewline` is set, we cut off the
 trailing newline of this given data before comparing with the one actually
@@ -673,6 +673,10 @@ comparisons are made.
 `crlf=yes` forces the newlines to become CRLF even if not written so in the
 test.
 
+`crlf=headers` forces *header* newlines to become CRLF even if not written so
+in the source file. Note that this makes runtests.pl parse and "guess" what is
+a header and what is not in order to apply the CRLF line endings appropriately.
+
 ### `<proxy [nonewline="yes"][crlf="yes"]>`
 
 The protocol dump curl should transmit to an HTTP proxy (when the http-proxy