FEATURE: targeted extra file transfers

I spent a lot of time thinking about !494 (closed) today and realized that the only stable behaviour is to specify the files that are needed on a sampler-by-sampler basis, it's boring, but I had a spare half hour to go through the various sampler outputs and write the required biolerplate. This avoids the potential problem of transferring lots of unnecessary files as would often happen with !494 (closed).

I've only tested this with dynesty so far, but it works well.

Ideally, longer term, we can make the paths for all of the checkpoint files uniform.