Update `naga_oil` to make use of `naga` frontend translation units.

After using `naga_oil` myself and running into some issues, I think it would really benefit having access to `naga` internals. I did search for this feature request within WGPU, but I originally did not find any other issues, so I opened my own (gfx-rs/wgpu#6250). It turns out there is also a similar issue at gfx-rs/wgpu#5713, and a more fitting issue gfx-rs/wgpu#6132. In both my issue and 6132, the green light was given to make a PR to expose some of the naga frontend translation units for use in other projects. I realised in mine it would make more sense to first try and update `naga_oil` to use `naga` before making the PR so there is a clear list of features that need to be publicized. I know this idea has been floating around some of this issues in this repo, is this definitely something that would still want to be implemented here? Although I couldn't start experimenting right now, I would be open to contributing to this change in the near future.