Establish cross-client validation suite.

[ruseinov]

Summary

As part of our last Retrospective we've been discussing the ability to use the same suite to test against Lotus, Forest and whatever else is going to implement the node RPC API.

This issue needs to be fleshed out further, however I'll share my vision for some of the steps:

1. Move RPC types from Forest to CommonNodeAPI in order to be able to:
   a. Have no dependency on Forest or any other big library here
   b. Be able to reuse RPC definitions for tests and Forest RPC implementation itself.
   NOTE: This will introduce extra burden similar to fil-actor-states where we'd have to define RPC types in one repo and then use them in Forest to define endpoints.
2. Inspire from Forest API tests that already knows how to test against various node implementations and move this into common-node-api.
3. Integrate RPC types and whatever else is needed back into Forest.

Motivation

We need a cross-client test suite for node RPC API. This is needed to make sure we can enforce the standard defined as part of common node API, use this in the CI for all the relevant projects and test our local changes.

Tasks

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Risks & Dependencies

Additional Links & Resources

[ruseinov]

cc @elmattic @ansermino I believe you guys are better equipped to take this further in terms of defining tasks and priorities here. That said, I'm happy to discuss any questions you might have on the subject in addition to what's already included in the description.