Pickle dump entire sampler in dynesty

We've noticed some pretty horrendous issues with restarting after a checkpoint recently.

I think that this is due to not saving all of the relevant state information.

This MR ensures the whole sampler will be saved.

I also took the liberty of adding two more plots.

• One is the run plot which dynesty produces, e.g.,
• The other is a little less pretty but shows the bound idx, number of likelihood calls and sampling scale as a function of the nested sampling iteration, e.g.,

The above plot shows the issue we had, the large spike followed by a higher nc steady state is when the run was interrupted and reloaded from the resume file (note that I stopped this run before it completely converged).

This is what that plot looks like with no interruption

This is what the plot looks like with the new checkpointing

bilby/core/sampler/dynesty.py

@@ -396,11 +396,6 @@ class Dynesty(NestedSampler):
         The check of whether the sampler is picklable is to catch an error
         when using pytest. Hopefully, this message won't be triggered during
         normal running.
-
-        Parameters
-        ----------
-        plot: bool
-            Whether to make plots showing the current state of the run
         """
         check_directory_exists_and_if_not_mkdir(self.outdir)
         end_time = datetime.datetime.now()