coderd tests use a lot of memory

[deansheather]

This does not seem like a normal amount of memory usage. On Sydney dogfood server this was using over 5GB of memory during a make test run:

[spikecurtis]

I mean, we spin up a whole Coderd with all the trimmings for basically every test case in that package. The API is huge now. We could really stand to subdivide it and convert our testing into unit tests for the smaller pieces.