Improve layout of annotation configuration dialogs

Summary:
The config dialog of each annotation tool is now a form layout without group boxes. Everything is aligned.

Reviewers: #okular, #vdg, ngraham, aacid

Reviewed By: #okular, #vdg, ngraham, aacid

Subscribers: sander, davidhurka, aacid, okular-devel, knambiar, ngraham

Tags: #okular

Maniphest Tasks: T8076

Differential Revision: https://phabricator.kde.org/D10859