New setting on "Table of files" and "Generic files" formatters to use files descriptions (or not)

Each time you upload a file, according to the field settings, you can also add a description.

Versions prior to Drupal 8.5.x only used that description to replace file names in the "Generic files" formatter, without giving the site builder the choice to do otherwise. The "Table of files" formatter never used the files' descriptions.

Now, both "Table of files" and "Generic files" formatters have an exposed use_description_as_link_text setting that allows to choose whether to replace the file name by the description or not. This setting is enabled by default.

To preserve backward compatibility, the upgrade path disables the setting for all existing "Table of files" instances.