Block Refresh: Use Spinner when ProgressBar component unavailable

[n7studios]

Summary

This PR replaced the spinner with the Gutenberg ProgressBar component, resulting in errors when clicking the refresh button within a block in WordPress < 6.3.

This PR resolves by using a spinner when the ProgressBar component is unavailable:

WordPress 6.2.8:

WordPress 6.9:

The refresh text within the button is also fixed:

Before:

After:

This PR also:

• runs backward compat. tests for blocks against WordPress 6.2.8, PHP 8.1
• uses a more generic selector when checking a block is refreshing
• uses a more generic selector when tests click the insert block button, to support WordPress 6.2.8 and higher

Testing

Existing tests pass.

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

[github-actions]

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[noelherrick]

I tried to figure out if there was a way to reuse some of this configuration from tests.yml, but it for now I don't think the juice is worth the squeeze since the reusable workflows really is more targeted to a workflow that can be parameterized with different env vars.