webtransport: check for UDP multiaddr component in address matcher

[Jorropo]

No description provided.

[marten-seemann]

Haven't reviewed the state machine carefully, but the table test looks rock solid.

[Jorropo]

The minimal diff is:

 ma.ForEach(multiaddr, func(c ma.Component) bool {
-		if c.Protocol().Code == ma.P_QUIC_V1 && state == init {
+		if c.Protocol().Code == ma.P_UDP && state == init {
 			state = foundUDP
 		}
 		if c.Protocol().Code == ma.P_QUIC_V1 && state == foundUDP {
 			state = foundQuicV1
 		}
 		if c.Protocol().Code == ma.P_WEBTRANSPORT && state == foundQuicV1 {
 			state = foundWebTransport
 		}
 		if c.Protocol().Code == ma.P_CERTHASH && state == foundWebTransport {
 			certhashCount++
 		}
 		return true
 	})

I thought switch was more readable.