h3-proxy: fixes around H3 proxy

code:
- less exception handling in existing code
- true ip happy eyeballing
- enable certificate verification
- cf-h2-proxy: abort connection when server closed connection

tests:
- remove all --insecure and --proxy-insecure args
- make session reuse test_60_12 a working one
- resolve port conflicts between h2o and nghttpx
- use proxy args better
- make test_60_06 run shorter
- kill h2o at the end of tests, normal stop takes too long

Ref: 59213f8248 #21789
Follow-up to e78b1b3ecc #21153

Closes #21798

lib/http_proxy.h

@@ -69,8 +69,8 @@ CURLcode Curl_http_proxy_inspect_tunnel_response(
 CURLcode Curl_cf_http_proxy_insert_after(struct Curl_cfilter *cf_at,
                                          struct Curl_easy *data,
                                          struct Curl_peer *dest,
-                                         uint8_t proxytype,
-                                         bool udp_tunnel);
+                                         uint8_t transport,
+                                         uint8_t proxytype);
 
 extern struct Curl_cftype Curl_cft_http_proxy;
 
@@ -83,4 +83,6 @@ extern struct Curl_cftype Curl_cft_http_proxy;
 
 #define IS_QUIC_PROXY(t) ((t) == CURLPROXY_HTTPS3)
 
+uint8_t Curl_http_proxy_transport(uint8_t proxytype);
+
 #endif /* HEADER_CURL_HTTP_PROXY_H */