lima/ppir: duplicate intrinsics in nir

lima/ppir: duplicate intrinsics in nir

Move the duplicate uniform and varying steps to a nir pass, along with
some changes in the duplicating strategy.

Node duplication is now done per user of the varying/uniform. This is
inspired by what the offline shader compiler seems to usually do, and as
usual aims to reduce register pressure and better utilize the ld_uni and
ld_var instruction slots.
It is worth noting that due to a bug/feature, ppir was already
duplicating uniforms per successor in ppir_node_add_src even if the
comment indicated it was meant to be per-block.
Additionally, ppir was duplicating load uniform nodes twice for nodes
that use the same uniform in more than one source, resulting in one
unnecessary (and unpipelineable) load. This new implementation in nir
only creates one load in that case.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Reviewed-by: Vasily Khoruzhick <anarsoul@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4535>