[Interface] Implement IGMP Version Support in Terraform Provider

[ChristopherJHart]

This PR adds support for configuring IGMP version (1-3) on various types of interfaces through the Cisco-IOS-XE-igmp YANG model. A new iosxe_interface_igmp resource supporting all interface types that support IGMP is added.

[danischm]

Do we expect a lot more attributes to be added here in the future? Otherwise it might not be worth creating a new resource and instead just add the version attribute to the existing iosxe_interface_* resources and data sources.

[ChristopherJHart]

I would say that yes, there's quite a few more interface-specific IGMP attributes that could be added in the future. Judging by the CLI options alone:

Switch(config)#interface Looopback0
Switch(config-if)#ip igmp ?
  access-group                IGMP group access group
  explicit-tracking           Enable/Disable IGMP explicit-tracking
  helper-address              IGMP helper address
  iif-starg                   IGMP update incoming interface field of starg
  immediate-leave             Leave groups immediately without sending last member query, use for one host network only
  join-group                  IGMP join multicast group
  last-member-query-count     IGMP last member query count
  last-member-query-interval  IGMP last member query interval
  limit                       IGMP limit
  mroute-proxy                Mroute to IGMP proxy
  proxy-report-interval       IGMP proxy report interval
  proxy-service               Enable IGMP mroute proxy service
  querier-timeout             IGMP previous querier timeout
  query-interval              IGMP host query interval
  query-max-response-time     IGMP max query response value
  static-group                IGMP static multicast group
  tcn                         IGMP TCN configuration
  unidirectional-link         IGMP unidirectional link multicast routing
  upstream-proxy              IGMP upstream IGMP proxy
  v3-query-max-response-time  IGMP v3 max query response value
  v3lite                      Enable/disable IGMPv3 Lite
  version                     IGMP version

In my opinion deriving from experience, there's quite a few of these options that are relatively popular and would likely be implemented into the provider eventually.

[danischm]

Considering this would be an interface scoped resource, which potentially is required on every interface in a chassis based switch, it could impact the overall number of resources significantly. Therefore we will add it to the existing interface resources for now.

27e46c8