http3 ConnContext regression in v0.43

[rthellend]

s.ServeQUICConn(conn) calls s.handleConn(conn),

handleConn(conn) wraps conn in an internal object "hconn":

hconn := newConnection(
		conn,
		s.EnableDatagrams,
		protocol.PerspectiveServer,
		s.Logger,
	)

which is eventually passed to ConnContext instead of the actual conn.

The expected behavior is to receive the original conn.

[rthellend]

ConnContext called with &http3.connection{Connection:(*netw.QUICConn)(0xc000159490), perspective:1, logger:(*slog.Logger)(nil), enableDatagrams:false, decoder:(*qpack.Decoder)(0xc0001fd020), streamMx:sync.Mutex{state:0, sema:0x0}, streams:map[protocol.StreamID]*http3.datagrammer{0:(*http3.datagrammer)(0xc000000280)}, settings:(*http3.Settings)(0xc0003a82f0), receivedSettings:(chan struct {})(0xc0000401e0)}

Where *netw.QUICConn is my own quic.Connection wrapper, which cannot be reached anymore.

[rthellend]

The fix would be something like:

	if s.ConnContext != nil {
-		ctx = s.ConnContext(ctx, conn)
+		ctx = s.ConnContext(ctx, conn.Connection)
		if ctx == nil {
			panic("http3: ConnContext returned nil")
		}
	}