REORG: http: move has_forbidden_char() from h2.c to http.h

REORG: http: move has_forbidden_char() from h2.c to http.h

Origin: https://git.haproxy.org/?p=haproxy-2.6.git;a=commit;h=4a776fd01560a8dfa7a57b30b4d5249c8da7b12c

This function is not H2 specific but rather generic to HTTP. We'll
need it in H3 soon, so let's move it to HTTP and rename it to
http_header_has_forbidden_char().

(cherry picked from commit d4069f3cee0f6e94afaec518b6373dd368073f52)
 [ad: backported for next patch BUG/MAJOR: h3: reject header values
 containing invalid chars]
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
(cherry picked from commit 21c4ffd025115058994a3e2765c17fc3cee52f90)
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
(cherry picked from commit 9c0bc4f201cf58c10706416cb4807c0f4794f8ac)
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
Gbp-Pq: Name REORG-http-move-has_forbidden_char-from-h2.c-to-http.patch