[HTTP/2] Enable curl tests

[c410-f3r]

The more tests, the better. curl has a nice suite so let's try make use of it without having to create a new backend.

It is already possible to simulate a curl binary in wtx-ui with the _curl feature, in other words, the basic infrastructure is already defined.

At the current time the curl.sh file is capable of executing ./runtests.pl but it seems that HTTP/1 is required.

$ .scripts/curl.sh

...
...
...

RUN: server/sws --pidfile "log/server/http_server.pid" --cmdfile "log/server.cmd" --logfile "log/http_server.log" --logdir "log" --portfile "log/server/http_server.port" --keepalive 30 --ipv4 --port 0 --srcdir "."
test 0001...[HTTP GET]

 1: protocol FAILED!
 There was no content at all in the file log/server.input.
 Server glitch? Total curl failure? Returned: 2

 - abort tests

Additionally, --disable-http breaks the build so I don't know the best way forward to only test HTTP/2.

./configure --disable-http --enable-debug --with-nghttp2 --without-ssl

cf-h2-proxy.c: In function 'tunnel_stream_init':
cf-h2-proxy.c:97:12: error: implicit declaration of function 'Curl_http_proxy_get_destination' [-Werror=implicit-function-declaration]
   97 |   result = Curl_http_proxy_get_destination(cf, &hostname, &port, &ipv6_ip);
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cf-h2-proxy.c:97:12: warning: nested extern declaration of 'Curl_http_proxy_get_destination' [-Wnested-externs]
cf-h2-proxy.c: In function 'submit_CONNECT':
cf-h2-proxy.c:958:12: error: implicit declaration of function 'Curl_http_proxy_create_CONNECT' [-Werror=implicit-function-declaration]
  958 |   result = Curl_http_proxy_create_CONNECT(&req, cf, data, 2);