REGTESTS: http-messaging: test the reporting of HTTP hardening results

REGTESTS: http-messaging: test the reporting of HTTP hardening results

This new test checks fs.hdng.found, fs.hdng.fixed, bs.hdng.found and
bs.hdng.fixed from a log-format, as well as the hdng_rej_name converter.
The same anomalies (underscore in a header name, unregistered header,
CTL in a trailer) are sent:
  - through the "trusted" profile on both sides: everything passes, and
    only "found" reports them;
  - in a request to a "strict" profile which deletes the two headers and
    rejects the trailer: the 400 is logged with the three rules in "fixed"
    and hdng_rej_name only names the reject. The trailers are sent apart so
    that the stream exists when they are rejected;
  - in a response from a server using the "strict" profile: same with a 502
    on the backend side;
  - in an H2 request with only the deleted headers: nothing is named.