selftests: net: bridge: add test for igmpv3 exc -> to_exclude report

The test checks for the following case:
    state          report        result                  action
  EXCLUDE (X,Y)  TO_EX (A)     EXCLUDE (A-Y,Y*A)        (A-X-Y)=Group Timer
                                                        Delete (X-A)
                                                        Delete (Y-A)
                                                        Send Q(G,A-Y)
                                                        Group Timer=GMI

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