[ENH] - Add functionality for managing sim params and simulating multiple signals together

[TomDonoghue]

In the Aperiodic Method project, I was simulating large groups of signals while both systematically iterating across parameter values and/or sampling from parameter distributions. In order to do so, I had to develop some utilities for managing simulation parameters and simulating groups of time series together.

This PR suggests adding that functionality directly into NDSP. It is all quite general, and I think fits well within the sim module. The code added here is basically the code that is demo'd in the aperiodic methods project here (which might be a good starting point to get a feel for how this approach looks / works): https://aperiodicmethods.github.io/notebooks/12-TimeSimsParameters.html

I've also sketched out some tutorials, which give a broad overview of the general approach / how this code works.

[ryanhammonds]

Looks good! I reviewed all the module code. I probably should've started with the tutorials to get a better sense of usage, so sorry if some of the comments lack foresight.

The tests are the only thing I didn't review. I can come back to those if you want. But since they pass / have coverage, I'm happy with them.

[TomDonoghue]

I think everything pertaining specifically to the updates here is addressed, so I'm going to merge this in now to move forward with integrating this new approach into a project. We should test this whole approach out a bit more before tagging the next version release.