More detailed logging of parallelization

[Jammy2211]

In the following issue, as user has had trouble being certain when things are running in parallel and how many threads are being used:

https://github.com/Jammy2211/PyAutoLens/issues/252

Would it be possible to have logging information present on this, immediately before a search starts (or during the search in perform_update, if checking things after it starts is a more robust assessment of what is and is not parallelized in the run?).