Deduplicate Material renderer function selection

[illwieckz]

That part of the Material code seems to be stable enough to start mutualizing some logic with the non-Material code.

The various ProcessMaterial*, BindShader* and UpdateSurfaceData* functions are selected at the same time the Render_* functions are, at q3shader parsing time.

This deduplicates many switch boilerplate and reduce risks to introduce discrepancies in the future when modifying some parts of the code and forgetting to report the same change everywhere else.