BUG/MINOR: hq-interop: support transcoding of absolute URI

BUG/MINOR: hq-interop: support transcoding of absolute URI

On the backend side, HTTP/0.9 transcoder is responsible to convert a HTX
request into a HTTP start line. In particular, path is generated from
the HTX request URI.

However, an absolute URI was not converted correctly in a HTTP/0.9
simple path. This occurs notably in most cases when using HTTP/2 or 3 on
the frontend side.

This issue was detected when running QUIC interop. Some servers
implementation such as picoquic would reject these requests as they are
considered invalid.

To adjust this, extract the path component from HTX uri using
http_uri_parser API.

This should be backported up to 3.3 as this is a QUIC backend fix.