ViewConfig: Add option to paste at cursor position by mouse

Summary:
With this option is the cursor not moved to the mouse position prior to
paste by middle click

BUG: 363492

Test Plan:

Reviewers: KTextEditor, dhaumann

Reviewed By: KTextEditor, dhaumann

Subscribers: cullmann, dhaumann, ngraham, kwrite-devel, kde-frameworks-devel, KTextEditor

Tags: Kate, Frameworks

Differential Revision: https://phabricator.kde.org/D17999