quic: http/3 getting server settings and customSettings

For applications such as webtransport, http settings are important for negotiating capabilities. The following problems may be present currently: 1.) I do not see a clear API path for a client that connects to a server to get the settings sent by the server. Looking at the C++ code, I think the available settings could be on the SessionTicket, However, if I immediately set a callback to onsessionticket after the Promise for QuicSession is fulfilled, I do not see a call. @jasnell : Is there another API path to get this information? Or is this a bug, if I do not see the callback? Then I will try to make a test. 2.) nghttp3 does not seem to support settings beyond the settings hardcoded in the library. I will query upstream about implementing a mechanism similar to the customSettings mechanism currently used for http2.