Tests: Run tests using ubuntu-latest

[n7studios]

Summary

Runs tests against ubuntu-latest, as ubuntu-20.04 will be deprecated: actions/runner-images#11101.

Moves creation of the nginx configuration within the GitHub action, and uses nginx's default /var/www/html folder for serving the WordPress site.

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)

[noelherrick]

@n7studios Tim, I was noticing we use a rather expansive permission grant for tests - should we match the recommended permission for WordPress plugins, such as setting it to read-only for the group and others? Thoughts?

[n7studios]

@n7studios Tim, I was noticing we use a rather expansive permission grant for tests - should we match the recommended permission for WordPress plugins, such as setting it to read-only for the group and others? Thoughts?

From memory, they were expansive for allowing Plugins to write to logs, and mainly to stop Codeception throwing some errors when trying to write to the tests/output folder when a GitHub action test fails. Let me review this and if less expansive permissions work, I'll submit then in a PR.