Add acceptance test harness

[BeigeBox]

This is a set of tests to exercise the code against an actual device. It lets us catch regressions that other tests may not, as well as make it easier for devs to test that their code didn't cause any unintended side effects. The intent is to make it so that PRs are higher quality. Note the README.md it explains it a bit more detail.

Pull Request Checklist

• The Rayhunter team has recently expressed interest in reviewing a PR for this.
  • If not, this PR may be closed due our limited resources and need to prioritize how we spend them.
• Added or updated any documentation as needed to support the changes in this PR.
• Code has been linted and run through cargo fmt.
• If any new functionality has been added, unit tests were also added.
• CONTRIBUTING.md has been read.

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[untitaker]

I think this is a good idea, but I think we should split this testsuite up into multiple based on required capabilities. It should be possible to run a subset of these tests without a working /dev/diag, and therefore add that subset to CI. Alternatively we could try to mock /dev/diag and drive its output from tests.

[BeigeBox]

I would be happy to do that, although I would also like to get buy in from the rest of the team before I spend more time working on this. It's been sitting for a month and if there's no interest from the folks doing the merging then it's not worth putting more time into it.

[cooperq]

I also think its worthwhile to have acceptance tests but this PR is too big to be reasonably reviewed. Would it be possible to commit the main wiring first and then the tests in smaller chunks?

[cooperq]

Closing this for now but to be clear I really do want this code! I just want it in smaller chunks please!