Use TimeProvider in M.E.Diagnostics.HealthChecks

I would love for these to be really deterministic though. So it'd even pass given a starved scheduler and whatnot. If you're feeling ambitious, you could kick the tires on the [new TimeProvider API](https://github.com/dotnet/runtime/issues/36617#issuecomment-1468661805). It was basically made for exactly this use case, so you wouldn't have to go and make your own custom abstraction. It was just merged 4 days ago, so it's not available quite yet in the aspnetcore repo, but it should arrive in the next SDK update which usually happens Monday. It's already available in the [latest installer](https://github.com/dotnet/installer#table).

_Originally posted by @halter73 in https://github.com/dotnet/aspnetcore/pull/42646#discussion_r1151263096_