OVN: Add IGMP SB definitions and ovn-controller support

OVN: Add IGMP SB definitions and ovn-controller support

A new IP_Multicast table is added to Southbound DB. This table stores the
multicast related configuration for each datapath. Each row will be
populated by ovn-northd and will control:
- if IGMP Snooping is enabled or not, the snooping table size and multicast
  group idle timeout.
- if IGMP Querier is enabled or not (only if snooping is enabled too), query
  interval, query source addresses (Ethernet and IP) and the max-response
  field to be stored in outgoing queries.
- an additional "seq_no" column is added such that ovn-sbctl or if needed a
  CMS can flush currently learned groups. This can be achieved by incrementing
  the "seq_no" value.

A new IGMP_Group table is added to Southbound DB. This table stores all the
multicast groups learned by ovn-controllers. The table is indexed by
datapath, group address and chassis. For a learned multicast group on a
specific datapath each ovn-controller will store its own row in this table.
Each row contains the list of chassis-local ports on which the group was
learned. Rows in the IGMP_Group table are updated or deleted only by the
ovn-controllers that created them.

A new action ("igmp") is added to punt IGMP packets on a specific logical
switch datapath to ovn-controller if IGMP snooping is enabled.

Per datapath IGMP multicast snooping support is added to pinctrl:
- incoming IGMP reports are processed and multicast groups are maintained
  (using the OVS mcast-snooping library).
- each OVN controller syncs its in-memory IGMP groups to the Southbound DB
  in the IGMP_Group table.
- pinctrl also sends periodic IGMPv3 general queries for all datapaths where
  querier is enabled.

Signed-off-by: Mark Michelson <mmichels@redhat.com>
Co-authored-by: Mark Michelson <mmichels@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
Acked-by: Mark Michelson <mmichels@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>