fix: cleanup html layer on component unmount

[lbendavid-cloudinary]

Pull request for cloudinary/frontend-frameworks

For which package is this PR?

@cloudinary/html @cloudinary/react

What does this PR solve?

Add a fix to ensure the html layer is still in use when trying to update the img element.

In React 18 in <StrictMode />, the lazyload plugin does not work as expected. The issue is that since the plugin's promise is being resolved after a new instance of HtmlImageLayer is created, the previous HtmlImageLayer is updating the img element with the src which is not the expected behavior.

Final checklist

• [ ] Implementation is aligned to Spec.
• [ ] Tests - Add proper tests to the added code.
• [ ] Relates to a github issue (link to issue).

[lbendavid-cloudinary]

@const-cloudinary i've added two tests, one for testing the "bad" behavior, and the second for the desired behavior