New Tabswitcher: Fix cut-off path strings
Summary:
...and add GUI test program for testing the TabswitcherFilesModel.
The reason was, that the truncating function used the Kate document name which can be "README.md (2)" where the " (2)" is appended to the filename. In these cases 3 characters were cut-off too much (see https://phabricator.kde.org/D16054).
Reviewers: Kate, dhaumann
Reviewed By: Kate, dhaumann
Subscribers: dhaumann, cullmann, kwrite-devel
Tags: Kate
Differential Revision: https://phabricator.kde.org/D16214