Migrate kernel and law tests to munit

[armanbilge]

This was the low-hanging fruit, just to dip our toe in the water.

[djspiewak]

Solid start. Nothing in here needs changing, just using the Request Changes to hold the merge.

I think we should do two things. First, munit somewhat infamously circumvents sbt's output buffers for essentially no reason, and it occasionally causes weirdness with other tasks. I always have to look up how @etspaceman fixed it and cargo cult from him, since I can never remember it. Second, I'd prefer not to be in a state where we have two simultaneous test frameworks in use within the project, so I think it's worth driving this to completion and merging it all at once.

[armanbilge]

First, munit somewhat infamously circumvents sbt's output buffers for essentially no reason, and it occasionally causes weirdness with other tasks.

Oh right that's extremely annoying. I've cargo-culted that too in various places, I'll make sure to bring that in.

Second, I'd prefer not to be in a state where we have two simultaneous test frameworks in use within the project, so I think it's worth driving this to completion and merging it all at once.

Fair enough!