No need to auto build rawimporter if we are building gluploader as it
will be always loaded on startup, but never used.
Skip the build of it when its meson option is set to "auto".
Add "clappergluploader" module which uses "glupload" and "glcolorconvert" internally,
allowing either uploading RAW system memory into GPU with GL colorspace conversion or
importing DMABufs into GL memory and making a GdkTexture out of them at one go.
