hello_xr Wayland graphics bindings are improperly initialized

See https://github.com/KhronosGroup/OpenXR-SDK/blob/master/src/tests/hello_xr/graphicsplugin_opengl.cpp#L106-L118

Wayland/xcb/xlib connections are all initialized to nonsense, and remaining fields (where applicable) are left entirely uninitialized. Testing on Monado seems to work anyway, at least on xlib, which further raises the question of whether this information is actually needed.

Read src/tests/hello_xr/graphicsplugin_opengl.cpp at lines 106-118 first, then trace how the Wayland, xcb, and xlib connection data is consumed. Done means the bindings no longer use nonsense or uninitialized fields, with the question of whether this information is needed resolved.

Written by the indexing model from the issue text.