Allow users to reorder or adjust dashboard sections

## Feature Description

As suggested at a recent WordCamp, allow users to reorder the sections of the Site kit dashboard, or even adjust in the form of accordions to minimize some sections.

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_Do not alter or remove anything below. The following sections will be managed by moderators only._

## Acceptance criteria

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## Implementation Brief

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### Test Coverage

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## QA Brief

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## Changelog entry

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The issue names no files, tests, or entry points. Start by locating the Site Kit dashboard implementation and clarify whether reordering, collapsible sections, or both are required. Define acceptance criteria and tests before implementation so the completed behavior can be verified.

Written by the indexing model from the issue text.