test: Minimal test suite to run against node RPC to check for breaks over the wire

[renaynay]

We need something ASAP that's minimal and covers the most important endpoints at first, and then spreads to 100% coverage of the API. We do not need the canonical API workstream to get this done, we can already do it now.

Spin up a node instance in docker and some separate sidecar-like program that uses node's API over RPC and ensures they're all working normally.

Run a mock tendermint node as well so the cel-node has something to point at for data, we need to test writes as well.

[renaynay]

Or let's maybe look at using knuu for this as a first step.