`public.worker.event` topic should be part of the public API

[rtuck99]

As per
https://github.com/DiamondLightSource/mx-bluesky/pull/1535/changes/BASE..4cdf50e81b84fbbf6181a02169bb4c5f3f421273#r2704626093

the public.worker.event topic used to publish events on the Stomp message bus should be made part of the public API, as in order to listen to published bluesky documents from blueapi you need to subscribe to it.