Describe the bug
Single-entry templates that already have an Entry created should not be visible in the list and should not be created.

To Reproduce
Steps to reproduce the behavior:

1. Open CMS
2. On the Welcome screen, click "Create New"
3. Click on Entry
4. Select a Single Entry Template
5. Notice a new Single Entry Template will be created. Even though we already have one.

Expected behavior
In the list, there should be two types of templates

1. Entries which are not Single Entry type
2. Entries that are Single Entry type but don't have an Entry created yet

However, we should make sure this is handled on the backend side as well. Ensuring a second single-entry creation is not possible.

Screenshots
If applicable, add screenshots to help explain your problem.

UI Version: 3.4.1
Backend Version: 3.1.8

Additional context
Add any other context about the problem here.