Add WorkflowUpdateResultException

[roxblnfk]

What was changed

Added the WorkflowUpdateResultException, which is thrown by UpdateHandle->getResult() when a Workflow Update Request is stuck in the ADMITTED status. This situation can occur when the Workflow neither accepts nor rejects the Update due to:

• No available workers
• Workflow Task fails in the same tick

Why?

Developers need to distinguish between null as an actual result of a Workflow Update action and "no result."
Prior to this patch, the code used assert($result === null), which did not align with reality. Additionally, assertions are typically disabled in production environments.

Checklist

1. Closes

2. How was this tested:

3. Any docs updates needed?

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Name	Status	Preview	Comments	Updated (UTC)
php	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 13, 2024 0:27am

[Sushisource]

@roxblnfk So I think we don't need to do this at all - in the other SDKs we just keep trying until we hit the timeout or are cancelled and we should mirror that behavior here.