T7621 vyos_firewall_global features (#432)

• t7621 vyos_firewall_global diff mode

• vyos_firewall_global integration test for diff

• enhanced integration tests with diff

• diff integration tests

• merged diff test

• 1.3- specific changes to integration tests

• data/config separated

Co-authored-by: Gaige B Paulsen <gaige@cluetrust.com>