gl/display: provide a gst_gl_display_new_with_type()
Allows more fine-grained control over the exact display type that is created.
Specifically, allows e.g. forcing a win32 (empty) display type instead of the automatically chosen egl if e.g. libgstgl is built against both wgl/gdi and egl/angle. Theoretically also allows choosing between cocoa and x11 on macOS if the XQuartz compatibility layer is installed.
Edited by Matthew Waters