Support for not throwing functions

[DanielZanchi]

Now it supports only functions that are throwing errors.
What about supporting function without try

[swhitty]

While the body closure () async throws -> T is throwing, it does support a closure that is not throwing like so;

let val = try await withThrowingTimeout(seconds: 2.0) {
   await perform()
}

withThrowingTimeout always throws because TimeoutError is always thrown when the deadline expires.