v0.20.0 - Remove server fallback and guarantee checks dont issue network request

When we first wrote local evaluation SDKs, we were worried about backwards compatibility for new conditions and operators, so we introduced a way to ensure backwards compatibility to old SDKs: issue a network request if the evaluation is inconclusive.

Fast forward, and we've realized this was a poor design decision. Good for backwards compatibility, but not worth the tradeoff and risk of potentially introducing a network round trip to every request.

We also now have evaluation metadata to surface if you try to evaluate something that is not supported on your SDK version to communicate the incompatibility in console.

Moving forward, our API will make a strong guarantee - all checks will be evaluated locally and will not issue a network request for evaluation.

Full Changelog: v0.19.1...v0.20.0