ref(tests): clean up and pare down test code

I moved the Go templates representing the test commands out of a JSON file into the test code, declared the commands and the exported test funcs at the top of each file, removed a vendored UUID library, and shortened several identifiers. These changes make the tests more approachable, so it's more reasonable to require the addition of tests along with future PRs.

I will add more code comments and a statement about requiring tests to our contributor docs in a separate PR; this one got big enough on its own.