foris-controller: update to version 2.1.0

This is intended as bugfix release, therefore it could go to TOS 5.3.x release (if there will be fix releases) or straight to %Turris OS 6.0.

Added:

• utils: add ip_network_address helper function

Changed:

• router_notifications: change default "from" and "host" of custom smtp server to empty string

Fixed:

• dns: fix setting custom forwarder port for non-TLS servers
• lan: update openvpn server push route configuration on lan update
• lan: fix crash on dhcp host which has multiple MAC addresses (contributed by ktetzlaff)
• lan: fix crash on negative dhcpv6 lease time; set it to 0 for now
• wan: add missing fw rule for 6to4
• zeroconf: Foris-controller won't fully start when something is running on port 5353