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

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.