Fix race condition when starting a local registry

[OneBlue]

Summary of the Pull Request

This change solves a timing issue by actually waiting for the newly created local registry to have the port bound before returning so the caller can immediately call into the registry

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 PR addresses flaky timing when starting the wslc-registry:latest test registry by centralizing registry startup logic in the shared e2e helpers and adding an explicit readiness wait before callers proceed.

Changes:

• Refactors StartLocalRegistry in the SDK tests (WinRT + COM) to delegate to WSLCE2ETests::StartLocalRegistry.
• Updates the shared WSLCE2ETests::StartLocalRegistry helper to wait for the registry init process to emit a “listening” message before continuing.
• Adds the shared helper header include to the affected test files.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
test/windows/WslcSdkWinRTTests.cpp	Delegates local registry startup to the shared e2e helper for consistent readiness behavior.
test/windows/WslcSdkTests.cpp	Delegates local registry startup to the shared e2e helper for consistent readiness behavior.
test/windows/wslc/e2e/WSLCE2EHelpers.cpp	Adds a pre-return readiness wait (based on init process output) to reduce registry startup race/flakiness.