pan/bi: Specialize shaders for IDVS

We need to compile multiple variants and report them together in a
common shader info. To do so, we split off per-variant shader infos and
combine at the end.

glmark2 is very happy: https://people.collabora.com/~alyssa/idvs-g52.txt
Highlights include -bshading up 41% fps and -bbump:bump-render=high-poly
up 62% faster

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <!14154>
47 jobs for !14154 with idvs-5 in 36 minutes and 37 seconds (queued for 29 seconds)
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