Update auto-renaming of linked files

[paudelritij]

Refs: JabRef/jabref#13295

Related: https://docs.jabref.org/finding-sorting-and-cleaning-entries/filelinks#filename-format-and-file-directory-pattern

[ThiloteE]

@paudelritij Would you mind doing the rewrite? You know the code the best. I really liked your PR by the way :-) I think it helps users a lot.

[paudelritij]

Thanks, I appreciate the feedback. I will take care of it.