[qpa] Use the new OpenGLContextAttributeBuilder to create Qt's OpenGL context

Summary:
Introduces a few more attributes needed for creating the OpenGL context
used by the QPA.

Test Plan:
Extended test and run KWin/Wayland and verified that OpenGL context
gets created correctly.

Reviewers: #kwin, #plasma

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D6734