[firewall] implement packet filtering in OT core (#9402)

This commit implements the packet logic in OT core. It aims to have
the same effect as what's already achieved by our iptables-based
firewall. Instead of leveraging iptables, this commit filters the
border routing packets in user space by checking the
source/destination addresses of a packet.

This commit also adds a job to do BR regression test when this feature
is enabled and iptables-based firewall is disabled.

script/test

@@ -342,6 +342,7 @@ do_build_otbr_docker()
         "REST_API=0"
         "WEB_GUI=0"
         "MDNS=${OTBR_MDNS:-mDNSResponder}"
+        "FIREWALL=${FIREWALL:-1}"
     )
 
     if [[ ${NAT64} != 1 ]]; then