proxy: http2 proxy tunnel implementation

- currently only on debug build and when env variable
  CURL_PROXY_TUNNEL_H2 is present.
- will ALPN negotiate with the proxy server and switch
  tunnel filter based on the protocol negotiated.
- http/1.1 tunnel code moved into cf-h1-proxy.[ch]
- http/2 tunnel code implemented in cf-h2-proxy.[ch]
- tunnel start and ALPN set remains in http_proxy.c
- moving all haproxy related code into cf-haproxy.[ch]

VTLS changes
- SSL filters rely solely on the "alpn" specification they
  are created with and no longer check conn->bits.tls_enable_alpn.
- checks on which ALPN specification to use (or none at all) are
  done in vtls.c when creating the filter.

Testing
- added a nghttpx forward proxy to the pytest setup that
  speaks HTTP/2 and forwards all requests to the Apache httpd
  forward proxy server.
- extending test coverage in test_10 cases
- adding proxy tests for direct/tunnel h1/h2 use of basic auth.
- adding test for http/1.1 and h2 proxy tunneling to pytest

Closes #10780

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/curl_log.c b/lib/curl_log.c
index 2301cff12..71024cfc6 100644
--- a/lib/curl_log.c
+++ b/lib/curl_log.c
@@ -38,6 +38,9 @@
 #include "connect.h"
 #include "http2.h"
 #include "http_proxy.h"
+#include "cf-h1-proxy.h"
+#include "cf-h2-proxy.h"
+#include "cf-haproxy.h"
 #include "cf-https-connect.h"
 #include "socks.h"
 #include "strtok.h"
@@ -160,6 +163,10 @@ static struct Curl_cftype *cf_types[] = {
 #endif
 #if !defined(CURL_DISABLE_PROXY)
 #if !defined(CURL_DISABLE_HTTP)
+  &Curl_cft_h1_proxy,
+#ifdef USE_NGHTTP2
+  &Curl_cft_h2_proxy,
+#endif
   &Curl_cft_http_proxy,
 #endif /* !CURL_DISABLE_HTTP */
   &Curl_cft_haproxy,