Update to `rustc_hash` v2

[andyleiserson]

With #8238, our dependencies are updated to use rustc_hash v2, but naga is still specifying rustc_hash v1. Switching is probably easy (although I haven't done any investigation to confirm that), but also seems like it's worth some diligence when we switch to check for performance regressions or other problems.

[cwfitzgerald]

I can't find it, but somewhere there is discussion about how rustc_hash v2 is a completely different algorithm. I think any changes would need to be motivated by performance; honestly hour current state of using rustc_hash at all (over any of the others) isn't well motivated by performance as it is.

[a1phyr]

Found it: #6999

[grovesNL]

For what it's worth we started with fxhash/rusct_hash because it was already used in WebRender and was a pretty common choice at the time gfx-rs/gfx#2148