Document workflow-friendly concurrency control

[drewhoskins-temporal]

Document and add tests confirming that asyncio.Lock and asyncio.Semaphore can be used to control interleaving of signal and update handlers and the main workflow coroutine.

[sreeprasannar]

does this mean currently using asyncio.Lock could lead to a deadlock?

[dandavison]

Hi @sreeprasannar

does this mean currently using asyncio.Lock could lead to a deadlock?

No -- using asyncio.Lock in sdk-python workflow code is appropriate and recommended.

Thanks! I've changed the title & wording of this ticket.

[drewhoskins-temporal]

temporalio/samples-python#123
temporalio/documentation#2959