feat(carousel): rename block and reorganise settings

[thomasguillot]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Similar to #1943, this time for the "Post Carousel" block.

How to test the changes in this Pull Request:

1. Add a bunch of Carousel Post blocks to a page with various settings
2. Switch to this branch
3. Check if the blocks are still displaying the correct information and has kept the correct settings

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?