fix(core): Fix validation of shader I/O numeric types

[andyleiserson]

For shader I/O:

• Inter-stage types must match exactly
• Fragment outputs only require that scalar kind matches. Scalar width may differ in either direction.

Fixes Firefox bug https://bugzilla.mozilla.org/show_bug.cgi?id=2013404 and part of #9143.

Testing
Enables CTS tests and adds a directed test.

Squash or Rebase? Squash

Checklist

• I self-reviewed and fully understand this PR.
• WebGPU implementations built with wgpu may be affected behaviorally.
• Validation and feature gates are in place to confine behavioral changes.
• Tests demonstrate the validation and altered logic works.
• CHANGELOG.md entries for the user-facing effects of this change are present.
• The PR is minimal, and doesn't make sense to land as multiple PRs.
• Commits are logically scoped and individually reviewable.
• The PR description has enough context to understand the motivation and solution implemented.