Add more ConnectionTest implementations

[Jeffail]

I decided to let claude code have a go at implementing ConnectionTest for a subset of our plugins because:

1. The implementations are mostly arbitrary, simply copying a subset of Connect and returning the appropriate response
2. This code isn't particularly hot, it will be used for diagnostic tooling and so it won't harm production environments if something is missed during review
3. It's otherwise going to take us centuries to have all of these implementations done

If this PR is well received then I'll be braver and try an even broader sweep of components.