[KDirOperator] Middle-elide labels that are too long to fit
Summary:
Right now too-long labels get right-elided, which among other minor issues, causes
their filename extentions to not be visible. Dolphin is moving to middle-eliding
labels instead (See D19471), so this patch implements the same behavior for KDirOperator
so the file dialogs behave the same way.
CCBUG: 404955
Test Plan: See the Test Plan in D19471; same deal
Reviewers: VDG, elvisangelaccio
Reviewed By: elvisangelaccio
Subscribers: kde-frameworks-devel
Tags: Frameworks
Differential Revision: https://phabricator.kde.org/D23201