Implement WGPU::{as, from}_core

[sagudev]

Connections
#10073

Description
Most of them are mechanical as they only have inner: DispatchType, the only two worth mentioning are TextureView which has Texture for subfield and Buffer which has mapping state, tho it is duplication of state wgc, but used for unsafe slicing so one needs to be careful with them.

Encoders are skipped because they are hard and I do not need them (hopefully).

I plan to use this to run wgpu libraries in trusted process on top of remoted wgc in servo. This was my main motivation for working on #5121 and #10073

Testing
None

Squash or Rebase?
Rebase

Checklist

• I self-reviewed and fully understand this PR.
• 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.
• (If applicable) WebGPU implementations built with wgpu may be affected behaviorally.
• (If applicable) Validation and feature gates are in place to confine behavioral changes.
• (If applicable) Tests demonstrate the validation and altered logic works.

[sagudev]

I would actually need this to write tests in #10307 so gentle nudge @cwfitzgerald