ILightWorker instances aren't discovered

[bruno-brant]

LightWorker works by discovering all classes that derive from it, then exploring methods annotated with Queue and Topic.

https://github.com/Avanade/Liquid-Application-Framework/blob/f4899e410442e6fe27858c16d4b32f6203444c9f/src/Liquid.Activation/Worker/LightWorker.cs#L85

However, the framework defines a ILightWorker. Since that class is never discovered, the interface is useless.

We have the option of either retiring ILightWorker or changing the discovery process to scan for it instead.