bluesearch.utils.find_files can be slow when doing regex

[jankrepl]

🐛 Bug description

We noticed that find_files can get really slow when we try to do recursive matching for a regex pattern.

It would be nice to investigate whether this could be improved

find_files(pathlib.Path("../neuroscience-literature/medrxiv/"), True, ".*\.meca$")

[jankrepl]

Note that this might be due to the fact that we are working on a mounted remote file system