nir: add nir_[fui]gt_imm and nir_[fui]le_imm helpers

nir: add nir_[fui]gt_imm and nir_[fui]le_imm helpers

These are similar to the nir_{cmp}_imm variants we already have, except
they negate the condition (apart from equality) and flip the arguments.
The reason we need this, is that we don't have all comparison directions
that would be required to always pass the immediate in the second
argument.

This allows us to create any comparison with an immediate without
having to manually create the immediate value.

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23460>