[Feature Request] Make startUpdate users aware that it's synchronous w/ worker

[drewhoskins-temporal]

Is your feature request related to a problem? Please describe.

See temporalio/features#469

sdk-php/src/Client/WorkflowStubInterface.php

Line 106 in 8cdcc18

public function startUpdate(string|UpdateOptions $nameOrOptions, ...$args): UpdateHandle;

wait stage is currently optional and the docstring implies it's async rather than sync

Describe the solution you'd like

Additional context

[roxblnfk]

With the release of 2.9.0, the method description was adjusted in such a way that the user would not be misled about the asynchronous operation of the method (#429).

We decided to force customers to explicitly pass in a flag saying what’s being awaited. (e.g. start_update(wait_for_stage=ACCEPTED/COMPLETED)) and then if they don’t provide it.

However, changing the method signature will lead to a breaking change.
We can add a method like startUpdateAsync in the future when WaitPolicy support it.