Create RFC for Zetaclient V2

[swift1337]

Describe the Issue
We need a unified, simple, fault-tolerant, and efficient chain orchestration logic in zetaclientd for chain observation. Let’s design one and elaborate on this in the RFC docs.

Expected Outcome
An RFC with components, diagrams, interfaces, and an explanation of the new zetaclient orchestration.

[lumtis]

I remove #1611 from the milestone and add this one.

Completing this document will give a clearer and more descriptive path toward a well structured ZetaClient codebase

[swift1337]

Related comment: #3139 (comment)