feature: add descriptive cli command output for 'set interface feature'

  DBGvpp# set interface feature local0 arp-foo arc bad-arc
  set interface feature: Unknown arc name (bad-arc)...

  DBGvpp# set interface feature local0 arp-foo arc arp
  set interface feature: Feature (arp-foo) not registered to arc (arp)...
  See 'show features verbose' for valid feature/arc combinations.

  DBGvpp# set interface feature local0 arp-disabled arc arp

Type: fix

Change-Id: I036bb2a75dd2d40f6901e4fde3eb14925238e19b
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>