Ability to specify prefered nodes for req/res protocols

[vpavlin]

This is a feature request

Problem

IIUC peers used for filter and lightpus are currently (for the most part) picked randomly. This is ok for most use cases, but it could be interesting to consider making it possible for devs to provider a "priority list" of nodes they want to use.

The reason for this might be they run a fleet of node that they primarilly want to be used in their application - to provide somewhat reliable quality of service and to not rely on potentially less reliable "random" peers.

This need would probably grow stronger with incentivization as well - devs might want to prioritize own nodes for traffic if the nodes get paid/rewarded.

Notes