Migrate some more QRegExps to QRegularExpression

Summary:
Please make a careful review. Many of these code
changes are most likely not touched by our unit tests, so
introducing regressions may happen quickly.

Test Plan: make test

Reviewers: cullmann

Reviewed By: cullmann

Subscribers: kwrite-devel, kde-frameworks-devel

Tags: Kate, Frameworks

Differential Revision: https://phabricator.kde.org/D9175