Disable zink fallback in EGL
    
    In mesa 23.3.x zink broke on nvidia, crashing in eglCreateContext.
    In the same release, zink was added as a fallback between the
    hardware drivers and swrast.
    Any application that was previously falling back to swrast
    now instead crashes, when using the nvidia vulkan driver.
    
    How exactly do you reach zink or previously swrast when using
    nvidia you may ask?
    One common path may be EGL applications using EGL_EXT_platform_xcb.
    The nvidia driver does not support it, thus GLVND tries the next
    driver which is mesa, mesa doesn't find any suitable hardware driver
    and thus falls back to zink or swrast.
    
    Until zink is stable again on nvidia, we should disable the zink
    fallback to prevent applications crashing instead of falling back
    to swrast.
    
    There should be no need to also disable the GLX fallback to zink
    as i'm not aware of a call path that would lead to using mesa when
    the nvidia drivers are installed.
    
    RHBZ 2255599
    RHBZ 2255768
    MESA 10340
    MESA 10341