Fix TemporalWorker::ExecuteAsync(Func<Task>) swallowing exceptions

[adeal]

What was changed

• Fix TemporalWorker::ExecuteAsync(Func<Task>) swallowing exceptions

Why?

The non-generic ExecuteAsync(Func<Task>) overload was using ContinueWith with TaskContinuationOptions.OnlyOnRanToCompletion. When the caller's task threw an exception, this option prevented the continuation from running, causing the continuation task to be canceled rather than faulted. This resulted in TaskCanceledException being thrown instead of the original exception (e.g., WorkflowFailedException).

Checklist

1. Closes [Bug] TemporalWorker::ExecuteAsync(Func<Task>) swallows exceptions, throws TaskCanceledException instead #599

2. How was this tested:
   Added regression test ExecuteAsync_PropagatesException.

3. Any docs updates needed?
   No.

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[cretz]

Thanks! Just one minor pedantic suggestion to simplify the test.

And don't forget to sign the CLA (link is above here in PR)

[cretz]

Ah yeah, it is confusing that .NET doesn't really have a "map-on-success" combinator and that continue-with inadvertently swallows failures here. Thanks for the fix!

I see one other place we'll need to fix this type of thinking (Temporalio.Workflows.Semaphore for a failure in a wait condition), but we can handle that in a separate issue, no worries.

[cretz]

One change needed, to use the existing shared environment instead of making a new one for just this test

[cretz]

@adeal - looks like some whitespace formatting failing in CI due to inadvertent commit to Semaphore.cs, can you remove that change? I opened #601 separately.