David Manouchehri
7625973ca1
Implement UDP tunneling over HTTP/3 using HTTP Datagrams (RFC 9297): - Add masque handler for server-side CONNECT-UDP - Add masque connector and h3-masque dialer for client-side - Add enableDatagrams option to HTTP/3 listener - Add shared utilities for datagram connections and path parsing Resource management and connection caching: - Add deferred stream cleanup in connector on error paths - Add IsClosed() and Close() methods to Client for proper session management - Clean up stale cached clients in dialer before reuse - Close underlying stream when DatagramConn is closed - Move RequestStream opening from connector to dialer to enable dead connection detection and cache invalidation (follows QUIC dialer pattern)