Fix image leaks in the tests causing failures in "WslcSdkTests::ImageProgressCallback"

[OneBlue]

Summary of the Pull Request

This change solves various image layer leaks in the tests that cause the WslcSdkTests::ImageProgressCallback to fail if ran from a storage of a previous test session.

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 updates the Windows WSLC SDK test suites to proactively delete registry-pulled images at test scope-exit, preventing leftover image layers from prior runs from contaminating subsequent runs (notably scenarios that exercise image pull progress callbacks).

Changes:

• Add scope-exit cleanup in WinRT-based image pull/auth tests to delete the test image via m_defaultSession.DeleteImage(...) (errors swallowed).
• Add scope-exit cleanup in C-API based image pull/auth tests to delete the test image via WslcDeleteSessionImage(...) (failures logged).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
test/windows/WslcSdkWinRTTests.cpp	Adds SCOPE_CLEANUP image deletion to avoid leaked images between WinRT test runs.
test/windows/WslcSdkTests.cpp	Adds wil::scope_exit_log image deletion to avoid leaked images between C-API test runs.