feat(ntp): enhances time sync with DHCP NTP and custom servers (#625)

* Ensure the mDNS mode is set every time network state changes

Eliminates (mostly) duplicate code

* Add custom NTP and HTTP time sync servers

Since the ordering may have been previously defaulted and saved as "ntp,http", but that was being ignored and fallback-defaults were being used, in Ordering, `ntp` means use the fallback NTP servers, and `http` means use the fallback HTTP URLs. Thus `ntp_user_provided` and `http_user_provided` are the user specified static lists.

* Add support for using DHCP-provided NTP server

network.go

@@ -19,6 +19,14 @@ func networkStateChanged() {
 	// do not block the main thread
 	go waitCtrlAndRequestDisplayUpdate(true)
 
+	if timeSync != nil {
+		if networkState != nil {
+			timeSync.SetDhcpNtpAddresses(networkState.NtpAddressesString())
+		}
+
+		timeSync.Sync()
+	}
+
 	// always restart mDNS when the network state changes
 	if mDNS != nil {
 		_ = mDNS.SetListenOptions(config.NetworkConfig.GetMDNSMode())