Improve the problems tool view CCBUG: 339839

Summary: Remove text in "Error", "Warning" and "Hint" buttons and move them from the pop-up menu. Add current scope setting to the "Scope" button.

Test Plan: Tests passed; works as expected.

Reviewers: kfunk

Reviewed By: kfunk

Subscribers: KDevelop, kdevelop-devel

Projects: KDevelop

Differential Revision: https://phabricator.kde.org/D799