[HTTP3] Implementation of range request in picohttp

[fbussery]

Right now picohttp doesn't provide the range request.
I did attached to this issue a quick implementation of the range request.
According to https://datatracker.ietf.org/doc/html/rfc9204#appendix-A
We just need to implement the qpack code 55

In the attached patch, I just did modify the api of h3zero.h to pass the range

Previous api was:

uint8_t * h3zero_create_post_header_frame_ex(uint8_t * bytes, uint8_t * bytes_max, uint8_t const * path, size_t path_length, char const * host, h3zero_content_type_enum content_type, char const* ua_string)

new
is

uint8_t * h3zero_create_post_header_frame_ex(uint8_t * bytes, uint8_t * bytes_max, uint8_t const * path, size_t path_length, 
uint8_t const * range, size_t range_length, char const * host, h3zero_content_type_enum content_type, char const* ua_string)

So, we can pass range this way for instance:
range = "bytes=100-1000" range_length = 14

I see no regressions with tests: picohttp_ct & picoquicdemo

Note that there is nothing right now in the code that check that range is accepted.

patch: 0001-Implementation-of-byte-range-according-to-rfc9204.patch.txt

[huitema]

See PR #1703 which is based on the patch. But we need to extend that PR to add actual support of ranges in the demo app, both on client and on server.