Improve StartWithContinuations test in AsyncType tests

[majocha]

Use a local cancellation token instead of Async.CancelDefaultToken() to cancel just one computation.

When running tests in parallel I've seen OperationCancelledException raised in unrelated tests of the same assembly.
It seems despite the fact this test collection has DisableParallelization = true, xUnit sometimes can't perfectly isolate the test cases.

ETA: It was me misconfiguring xUnit exclusions.
Still, I think this looks a bit cleaner.

[github-actions]

✅ No release notes required

[majocha]

New version goes like this:

moduleAsyncType =typeExpectedContinuation= Success | Exception | Cancellation
[<Fact>]letstartWithContinuations()=letcont actual expected _ =if expected <> actual then
failwith $"expected {expected} continuation, but ran {actual}"letonSuccess= cont Success
letonExeption= cont Exception
letonCancellation= cont Cancellation
letexpect expected computation =
Async.StartWithContinuations(computation, onSuccess expected, onExeption expected, onCancellation expected)async{
Async.CancelDefaultToken()return()}|> expect Cancellation
async{ failwith "computation failed"}|> expect Exception
async{return()}|> expect Success

[psfinaki]

Okay I think I've verified the equivalence, thanks for the refactoring, it definitely looks clearer now.