Rework of wgpu_hal vulkan buffer importing

[SupaMaggie70Incorporated]

Connections
Discussed briefly with @cwfitzgerald in matrix chat.

Description

• Moved wgpu_hal's vulkan buffer constructor to the buffer type
• Added from_raw_managed, so that the buffer's memory can be managed by wgpu rather than externally

Testing
Currently no testing. I don't believe there is any testing for the existing work either however.

Squash or Rebase?

Either works, there is only one commit at the moment.

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy --tests. If applicable, add:
  • --target wasm32-unknown-unknown
• Run cargo xtask test to run tests.
• If this contains user-facing changes, add a CHANGELOG.md entry.