[Custom Components] - Allow custom components to register custom Actions

[poirazis]

The scenario is to allow custom components to expose custom actions they respond to, possibly only for self hosted
The scenario is i have created an MQTT component and i would like to register an action "Publish MQTT Message" that would allow other components to instruct the component to publish a message.

The only way to achieve this currently is via a State variable ( react when the variable changes, and publish the contents of that variable ) or higjack another action ( which is way too hackish )

[linear]

BUDI-8956 [Custom Components] - Allow custom components to register custom Actions