Review "Polly" approach

[bruno-brant]

Polly is a resilience library for .NET. It was somewhat coupled to Liquid (the name of the interface is ILightPolly, for instance).

Right now, for some unknown reason, WorkBench.Polly is different to other cached services, in that Polly is a public property, and it is written to by UseBase:

https://github.com/Avanade/Liquid-Application-Framework/blob/f2b5da239bd9f411386344053989609abcb4f1ce/src/Liquid.Middleware/UseBase.cs#L78

Well, that's a bit strange. It seems that all the protections of other services, such as not being able to set them twice, is lost...

We should rethink this approach.

[bruno-brant]

Marking this issue as a discussion because we still need to design how Polly should be added to the framework.