Refactor all the linking code with the following objectives:
* Remove linking magic (especially around XFB)
* Cleaner code (obviously)
* Less stage coupling (in case someone ever implements geom/tess)
* Decouple ATTRIBUTE from ATTRIBUTE_BUFFER to enable optimizations
The main hack remaining is doing precision linking here to workaround
linking previously used.
Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10778>