Adapt to wlroots and Plasma workspace changes

This MR fixes problems resulting from changes in upstream wlroots and downstream Plasma workspace.

Compilation

• Adapt to changed DRM leasing API in wlroots.

Runtime

• Fix Plasma OSD positioning on X11.
• Get the DRM fd from wlr_renderer as otherwise we might run into GEM ref'counting issues.
• Adapt to wlroots change requiring us to create renderer and allocator ourselves.

The wlroots changes must be backportet to the 5.23 release in case wlroots 0.15 is released before the next Plasma release in February.

Closes #214 (closed)