Rework Connect Eyeballing, HTTP/2 and HTTP/3 connection filters

[icing]

Refactoring of connection setup and happy eyeballing. Move nghttp2. ngtcp2, quiche and msh3 into connection filters.

• eyeballing cfilter that uses sub-filters for performing parallel connects

• socket cfilter for all transport types, including QUIC

• QUIC implementations in cfilter, can now participate in eyeballing

• connection setup is more dynamic in order to adapt to what filter did really connect. Relevant to see if a SSL filter needs to be added or if SSL has already been provided

• HTTP/3 test cases similar to HTTP/2

• multiuse of parallel transfers for HTTP/3, tested for ngtcp2 and quiche

• Fix for data attach/detach in VTLS filters that could lead to crashes during parallel transfers.

• Eliminating setup() methods in cfilters, no longer needed.

• Improving Curl_conn_is_alive() to replace Curl_connalive() and integrated ssl alive checks into cfilter.

• Adding CF_CNTRL_CONN_INFO_UPDATE to tell filters to update connection into and persist it at the easy handle.

• Several more cfilter related cleanups and moves:

  • stream_weigth and dependency info is now wrapped in struct Curl_data_priority
  • Curl_data_priority members depend is available in HTTP2|HTTP3
  • Curl_data_priority members depend on NGHTTP2 support
  • handling init/reset/cleanup of priority part of url.c
  • data->state.priority same struct, but shallow copy for compares only

• PROTOPT_STREAM has been removed

  • Curl_conn_is_mulitplex() now available to check on capability

• Adding query method to connection filters.

  • ngtcp2+quiche: implementing query for max concurrent transfers.

• struct http is now empty in easy handles, could be removed

• Adding is_alive and keep_alive cfilter methods. Adding DATA_SETUP event. - setting keepalive timestamp on connect - DATA_SETUP is called after the connection has been completely setup (but may not connected yet) to allow filters to initialize data members they use.

• there is no socket to be had with msh3, it is unclear how select shall work

• manual test via "curl --http3 https://curl.se" fail with "empty reply from server".

• Various socket/conn related cleanups:

  • Curl_socket is now Curl_socket_open and in cf-socket.c
  • Curl_closesocket is now Curl_socket_close and in cf-socket.c
  • Curl_ssl_use has been replaced with Cur_conn_is_ssl
  • Curl_conn_tcp_accepted_set has been split into Curl_conn_tcp_listen_set and Curl_conn_tcp_accepted_set with a clearer purpose

[bagder]

Thanks!