Expose UpdateID in an update handler

[drewhoskins-temporal]

This will allow users to use it when they want a unique idempotent primary key for handlers.

[roxblnfk]

Looks like we already have it

sdk-php/src/Client/Update/UpdateHandle.php

Lines 45 to 48 in cc87986

	/**
	* Gets the unique ID of this update.
	*/
	public function getId(): string

[cretz]

I think that is for the client. This is for access inside the handler inside the workflow. Go is using context for this, other languages are using "async local" or similar. Unsure the best approach in PHP for providing contextual state to a handler (and things it may start) without affecting anything outside the handler.

[roxblnfk]

This is for access inside the handler inside the workflow

Got it. Thanks.