Fix Error of This entity cannot be referenced when Entity Queue has unpublished node

Problem/Motivation

After creating an Entity Queue, if a node is added to the queue and later on that node is changed to unpublished, in this case the whole Entity Queue remains non editable and it shows this error 'This entity cannot be referenced'. This is because the node is not automatically removed from the Entity Queue, also you cannot remove it manually (same error shows up)

Proposed resolution

When Adding entity to all checked queues.
If the node was unpublished, do not attempt to add it to any entity queue.

When Removing entity from all un-checked queues.
If the node was unpublished, remove it from all enabled entity queues.

Remaining tasks

• ✅ File an issue
• ✅ Addition/Change/Update/Fix
• ✅ Testing to ensure no regression
• ➖ Automated unit testing coverage
• ➖ Automated functional testing coverage
• ➖ UX/UI designer responsibilities
• ✅ Readability
• ✅ Accessibility
• ➖ Performance
• ➖ Security
• ➖ Documentation
• ✅ Code review by maintainers
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Release notes snippet
• ✅ Release entityqueue_form_widget-2.0.6

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• Issue #3226254 by Ahmad Smhan: Fixed Error of This entity cannot be referenced when Entity Queue has unpublished node