nir: introduce and use nir_component_mask

nir: introduce and use nir_component_mask

The BITFIELD_MASK() macro is intended for using with actual bitfields,
not with nir_component_mask_t. This means we do some extra work to
handle values that are invalid for nir_component_mask_t in the first
place.

This eliminates some warnings on Clang, where the compiler complains
about casting UINT32_MAX to UINT16_MAX.

Reviewed-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15547>