Enhance functionality related to pgws and fips to be oblivious to specific cidr

[ShiriMoran]

A pgws/fips are network interface dependent, and are oblivious to the exact cidr of an external address.
Certain functionality, as AllowedConnectivity(src, dst Node) *common.ConnectionSet of RoutingResource requires two Nodes, which specifies specific cidr.
The relevant functionality needs to be enhanced to be oblivious to the exact cidr and be dependent only in the specific network interface and the same for all external addresses.

(see #320 (comment))

[adisos]

will be resolved by PR #372

Required update for explainability computation - avoid calling getContainingConfigNode for the input nodes of getRoutingResource

[adisos]

opened small PR to update explainability code: #383