#22749 broke release unit tests by not providing a legacy key - that key should be optional because we will b dealing with non-legacy tests soon.
Additionally, for some reason the unit tests pass on buildkite while they fail locally and in the release test pipeline. I'm investigating this now...
Of all smoke test arguments, frequency is the only required one, so we should check for it. Additionally, not all fields should be able to be overwritten (e.g. legacy or name), so we enforce this as well.
To avoid breakage like in #22905, this PR adds schema validation to the release test package.
In a follow-up PR, we'll likely switch this to use pydantic instead.
