[core] Inherit InstanceFlags in Device via Adapter

[sagudev]

Connections
As noted in #9901 (comment)

Description
Before wgc users needed to manually pass instance flags to request_device/create_device_and_queue_from_hal. We do not override them anywhere so we should just make them inheritable through Instance -> Adapter -> Device.

Testing
Just refactor

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.

[Wumpf]

nice, less error prone too!