Remove ALPN Muxer (#1965)

We never ended up using this and it makes it much harder to reason about the listeners.

An explanation: for the moment I separated out all of the listeners in the struct, even though one should suffice, because when I did it that way first I was hitting some really weird and hard to find intermittent behavior where it seemed like the listeners were getting crossed. So I re-did it this way with each listener very explicitly referenced. I'm happy to make a follow-up PR that attempts to combine them all into a single listener without hitting the issues I did, if desired, but at least doing it via a separate PR means that it won't be something with removing the ALPN muxer that is at fault.

internal/servers/controller/testing.go

@@ -219,7 +219,15 @@ func (tc *TestController) addrs(purpose string) []string {
 	addrs := make([]string, 0, len(tc.b.Listeners))
 	for _, listener := range tc.b.Listeners {
 		if listener.Config.Purpose[0] == purpose {
-			addr := listener.Mux.Addr()
+			var addr net.Addr
+			switch purpose {
+			case "api":
+				addr = listener.ApiListener.Addr()
+			case "cluster":
+				addr = listener.ClusterListener.Addr()
+			case "ops":
+				addr = listener.OpsListener.Addr()
+			}
 			switch {
 			case strings.HasPrefix(addr.String(), "/"):
 				switch purpose {