core: Use port ranges to avoid OOM with bad inputs (#2859)

* fix OOM issue caught by fuzzing

* use ParsedAddress as the struct name for the result of ParseNetworkAddress

* simplify code using the ParsedAddress type

* minor cleanups

listeners_fuzz.go

@@ -18,7 +18,7 @@
 package caddy
 
 func FuzzParseNetworkAddress(data []byte) int {
-	_, _, err := ParseNetworkAddress(string(data))
+	_, err := ParseNetworkAddress(string(data))
 	if err != nil {
 		return 0
 	}