Add and use a `naga_oil` macro to abstract over material texture sampling shader code

[alice-i-cecile]

Yeah, I'd love a macro in naga_oil. We could do a lot with macros, not just [meshlets/normal code paths]. For example, we could abstract over bindless/non-bindless declarations.

Originally posted by @pcwalton in #16644 (comment)

[JMS55]

@alice-i-cecile suggestion to edit the issue title: "to abstract over material texture sampling shader code"