http3: initial support for OpenSSL 3.2 QUIC stack

- HTTP/3 for curl using OpenSSL's own QUIC stack together
  with nghttp3
- configure with `--with-openssl-quic` to enable curl to
  build this. This requires the nghttp3 library
- implementation with the following restrictions:
  * macOS has to use an unconnected UDP socket due to an
    issue in OpenSSL's datagram implementation
    See https://github.com/openssl/openssl/issues/23251
    This makes connections to non-reponsive servers hang.
  * GET requests will send the indicator that they have
    no body in a separate QUIC packet. This may result
    in processing delays or Transfer-Encodings on proxied
    requests
  * uploads that encounter blocks will use 100% cpu as
    detection of these flow control issue is not working
    (we have not figured out to pry that from OpenSSL).

Closes #12734

lib/curl_setup.h

@@ -827,6 +827,7 @@ int getpwuid_r(uid_t uid, struct passwd *pwd, char *buf,
 #endif
 
 #if (defined(USE_NGTCP2) && defined(USE_NGHTTP3)) || \
+    (defined(USE_OPENSSL_QUIC) && defined(USE_NGHTTP3)) || \
     defined(USE_QUICHE) || defined(USE_MSH3)
 #define ENABLE_QUIC
 #define USE_HTTP3