Currently naga tests are part of the naga crate. This means that a lot of tests are dependent on features being enabled. This is a very easy gottcha as you run cargo nextest run it runs a few tests, but not convert_wgsl and the other big ones, as they need wgsl-in. If we move them to their own crate, we can have the tests require the features they need, ensuring that a default run gets all of the tests.