Optimize ArchiveModel::cleanFileName

Summary: Creating the QRegularExpression is expensive and cleanFileName is called for each entry. By not re-creating the regex we gain a significant archive load time improvement

Test Plan:

Left is before, right is after. Note the red block on the left that isn't present on the right

Reviewers: Ark, elvisangelaccio

Reviewed By: Ark, elvisangelaccio

Subscribers: elvisangelaccio, kde-utils-devel

Tags: Ark

Differential Revision: https://phabricator.kde.org/D25565