Use `Ouroboros.Consensus.Node.run` in protocol tests

At the moment, the protocol tests define their own run method. This means that the top-level function we export to run the node falls outside the scope of our tests, which is bad.

Unfortunately, using it directly will mean that we need to generalize it in various ways, so this is not entirely trivial. However, it is important to catch bugs such as https://github.com/input-output-hk/ouroboros-network/pull/2031.