selftests: net: bridge: add vlan mcast snooping control test

selftests: net: bridge: add vlan mcast snooping control test

Add the first test for bridge per-vlan multicast snooping which checks
if control of the global and per-vlan options work as expected, joins
and leaves are tested at each option value.

TEST: Vlan multicast snooping enable                                [ OK ]
TEST: Vlan global options existence                                 [ OK ]
TEST: Vlan mcast_snooping global option default value               [ OK ]
TEST: Vlan 10 multicast snooping control                            [ OK ]

Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>