Retry to delete distribution VHD for up to 10 seconds

[Blue (OneBlue)]

Summary of the Pull Request

This change adds logic to retry deleting WSL distribution VHDs for up to 10 seconds. We've seen test failures caused by that file being in used during un-registration.

PR Checklist

• Closes: Link to issue #xxx
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

[Copilot]

Pull request overview

This pull request improves the robustness of WSL distribution un-registration by retrying deletion of the distro VHD when the file is temporarily in use (e.g., due to sharing violations), reducing intermittent test failures during cleanup.

Changes:

• Replace single-attempt VHD deletion with a bounded retry loop (100ms interval, up to 10 seconds).
• Retry only on ERROR_SHARING_VIOLATION, logging the failure after the timeout expires.