Provide HTTP Client Version discovery mode for HTTP/3

**Jetty version(s)**
12.1.10

**Enhancement Description**
According to https://jetty.org/docs/jetty/12.1/programming-guide/client/http.html#transport-dynamic:

> HTTP/1.1 and HTTP/2 are compatible because they both use TCP, while HTTP/3 is incompatible with previous HTTP versions because it uses QUIC.

> Only compatible HTTP versions can negotiate the HTTP protocol version to use via ALPN, and only compatible HTTP versions can be upgraded from an older version to a newer version.

OTOH the Java HTTP Client uses some built-in discovery mode described in https://docs.oracle.com/en/java/javase/26/docs/api/java.net.http/java/net/http/HttpOption.Http3DiscoveryMode.html#ANY to figure out if HTTP/3 is supported by the server.

This is related to https://github.com/jetty/jetty.project/issues/11407 however this is not relying on `Alt-Svc` header being returned from an HTTP 1/2 request but rather about trying the connection in advance via both TCP and UDP (QUIC) in parallel and use the one which first returns.

Start with Jetty's HTTP client transport-dynamic documentation and the related issue #11407, then compare the requested behavior with Java's HttpOption.Http3DiscoveryMode documentation. Done means defining and implementing a discovery mode that attempts TCP and QUIC connections in parallel and uses whichever succeeds first, without relying on Alt-Svc.

Written by the indexing model from the issue text.