Change CSV file upload location to private://

This changes also the temporary://path_redirect_import/migrate.csv in the migrate yaml config

Confirmed it works as expected. Note that the file_cron removes unused files marked as temporary in the private directory by default.

I agree with jaapjan → . It works as expected.

The patch from #3 works as expected on Drupal 10.2.2 and Path redirect import 2.0.9

I can confirm it also works on Drupal 10.3.10 and Path redirect import 2.1.0!

Confirmed this works perfectly in Drupal 10.4.3 and Path Redirect import v.2.1.0. Thanks for the work on this patch!