[MOOSE-368] BE: Fix Admin Menu Order

[GeoffDusome]

What does this do/fix?

This pull request refines the logic for retrieving post type subscribers in the admin menu order functionality. The main change is to improve how post type subscribers are filtered and which ones are skipped, making the code more efficient and accurate.

Improvements to post type subscriber filtering:

• Updated the filtering in get_post_types() to only include subscribers containing 'Post_Types\', using array_filter for better clarity and efficiency.
• Refined the list of post type subscribers to skip by specifying the full class names (e.g., 'Tribe\Plugin\Post_Types\Page\Page_Subscriber') instead of generic post type names, ensuring only the intended subscribers are excluded.

QA

Links to relevant issues

• Link to Issue

Screenshots/video:

• Admin Menu Order in tact: https://p.tri.be/i/zmbZcp

Pull request checklist

• I've added a changelog entry for these changes.
• I've linked to a relevant Jira issue.
• I've captured a screenshot or screencast of the changes and linked it above.

[dpellenwood]

🍏