[kimpanel] Port settings page to QQC2+Kirigami FormLayout and modernize UI
Summary:
- Port to QQC2+Kirigami FormLayout
- Improve some strings
- Follow the KDE HIG
- Improve look of controls
Test Plan: Open the Input Method Panel widget settings.
Reviewers: Plasma, VDG, ngraham
Reviewed By: VDG, ngraham
Subscribers: ngraham, VDG, plasma-devel, Plasma
Tags: Plasma
Maniphest Tasks: T10586
Differential Revision: https://phabricator.kde.org/D20906