Allow NavList to paginate multiple groups

[strackoverflow]

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Please read this description carefully. If you feel there is anything unclear or missing, please ask for updates.

What are you trying to accomplish?

This PR moves the "show more" pagination to the NavList group level, allowing each group to receive pagination within a NavList. Previously, only the first group would receive pagination.

Demo

navlist.mov

Integration

This change shouldn't break existing usage of "show more", and when this change is integrated into GitHub dotcom we can remove the local workaround to allow pagination in the left-hand global side panel groups.

List the issues that this change affects.

Closes #1885

Risk Assessment

• Low risk the change is small, highly observable, and easily rolled back.
• Medium risk changes that are isolated, reduced in scope or could impact few users. The change will not impact library availability.
• High risk changes are those that could impact customers and SLOs, low or no test coverage, low observability, or slow to rollback.

What approach did you choose and why?

I largely implemented the same workaround that I did when we added pagination to the NavList in dotcom's global side panel, which is pulling all "show more" related code out of the nav-list element and into a new nav-list-group element. With that change, each group can now manage its own pagination state.

Anything you want to highlight for special attention from reviewers?

1. I added some more sample "foods" to differentiate the two NavList groups in the Lookbook preview, with the second group fetching up to four pages of items and the first group only fetching two. I stuck with the Futurama theme 😄
2. Does the focusMarkers behavior still work as expected with this change? It seems like it to me but it's worth double-checking.

Accessibility

• No new axe scan violation - This change does not introduce any new axe scan violations.

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Lookbook)
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge

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[changeset-bot]

🦋 Changeset detected

Latest commit: f4cc085

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/view-components	Patch

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[github-actions]

⚠️ Visual differences found

Our visual comparison tests found UI differences. Please review the differences by viewing the files changed tab to ensure that the changes were intentional.

Review visual differences

[jonrohan]

Looks like there's a failing system test

[camertron]

This is looking great! Just that one system test issue, but I'm a soft 🚢

[strackoverflow]

Thanks @jonrohan & @camertron - that system test that I missed has been updated!