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?

[dkoo]

This needs a little updating to more closely match changes made in #2000:

• Rename "Settings" panel to "Display"
• Rename "Loop" panel to "Content"
• Move "Display" panel below "Content" panel

These changes would bring the sidebar panels more in line with changes to the Content Loop block in #2000.

Aside from that, there are some additional changes we could consider to this block, either in this PR or another one. Consider these non-blocking suggestions rather than required changes.

• Add option to "Allow duplicate stories" or not, and make sure it works the same way in both editor vs. front-end (see comment for details on how it's currently slightly broken)
• Consider moving attributes from index.js to a block.json file for registering block attributes, to bring it in line with other blocks in our codebase