Fix issues on WordPress 6.7 and 6.8

[dkotter]

Description of the Change

After merging in #135, noticed that some E2E tests were failing on develop. In investigating, found a few issues that this PR fixes:

• In WordPress 6.8, the markup of the Start Page modal has changed, so code updates were needed in our createPost command to ensure that is closed properly
• Also in WordPress 6.8, there's a new template editing mode that is the default when creating pages. This breaks the insertion of content so we now switch that mode off when a page is created using the createPost command
• There were a few tests failing since WordPress 6.7 due to the sticky toggle being moved
• We weren't properly running tests on 6.7 so the matrix we run tests on has been updated. In addition, properly marking the trunk version as trunk, instead of hardcoding that to a version number, since the actual version number for trunk will change anytime a new release comes out

How to test the Change

Ensure E2E tests are passing here

Changelog Entry

Fix - Ensure the createPost command works properly when used to create pages on WordPress 6.8 Developer - Update the matrix of WordPress versions we run our E2E tests on Developer - Ensure all E2E tests pass on WordPress 6.7

Credits

Props @dkotter

Checklist:

• [x] I agree to follow this project's Code of Conduct.
• [ ] I have updated the documentation accordingly.
• [ ] I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• [x] All new and existing tests pass.