nir: Remove integer and 64-bit modifiers

nir: Remove integer and 64-bit modifiers

Now that Intel and R600 both do their own modifier propagation, the only
backends that still lower modifiers in NIR are:

* nir-to-tgsi
* lima
* etnaviv
* a2xx

The latter 3 backends do not support integers, and certainly do not support
fp64. So they don't use these.

TGSI in theory supports integer negate modifiers but NTT doesn't use them, so
they're unused there too.

Since they're unused, we remove NIR support for integer and 64-bit modifiers,
leaving only 16/32-bit float modifiers. This will reduce the scope needed for a
replacement to NIR modifiers, being pursued in !23089.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Reviewed-by: Christian Gmeiner <cgmeiner@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23782>