feature: introduce feature arc end nodes

This change allows us to keep feature path disabled
until 1st feature is enabled. Enabling 1st feature also means
that end feature node is enabled helping feature arc tenants
to reach the end.

Change-Id: Idbd64e681bd2b42e7c67612074649e5ae51f46e6
Signed-off-by: Damjan Marion <damarion@cisco.com>