Add default node descriptors

[clandest]

If we want to achieve mass adoption of MASQ, we need to make it very user friendly with convention over configuration in mind. Forcing the user to find a node descriptor and copy/paste it is a blocker.

Proposed solution is to run some official node descriptors, which will be by default pre-filled in MASQ client. Or alternative solution, is to implement some algorithm that will pre-fill the most suitable Node descriptor to maintain network health or stability or the one that will be fastest for the user.

[kauri-hero]

This is currently achieved using APIs that are semi-public and read-only