selftests: mlxsw: Add a test for VxLAN configuration with a VLAN-aware bridge

Extend the existing VLAN-unaware tests with their VLAN-aware
counterparts. This includes sanitization of invalid configuration and
offload indication on the local route performing decapsulation and the
FDB entries perform encapsulation.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>