spirv: Deal with glslang not setting NonUniform on constructors.

spirv: Deal with glslang not setting NonUniform on constructors.

Especially a problem for OpImage/OpSampledImage. Note that the problem
doesn't seem to be propagation through glslang, but only in emitting
the SPIR-V. So it is fine if we are somewhat lossy in handling this, as
long as direct Op(Sampled)Image -> texture op chains work.

Fixes: af81486a8cd "spirv: Simplify our handling of NonUniform"
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/3406
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6451>