Add Decorate extension method

[kzu]

Given this feature isn't moving forward fast enough on the runtime side, perhaps we should just bring something like this version into our project.

I think decorating could potentially be its own "pipeline" like the one in MEAI for IChatClient, which you can think of decorators too in a way. So the mechanism used there (returning a builder where its Build method returns the final object to be registered as the service) might work well here too.

[abatishchev]

Scrutor already has this feature, btw. Perhaps, it's the only feature it has :-D