chore: move release notes folder and v0.52 release notes

[heitortsergent]

What?

Move the Release notes page from the Misc section to the top-level section, and add the release notes for the v0.52.0 of k6.

This change makes it consistent with the other Grafana products.

Checklist

• I have used a meaningful title for the PR.
• I have described the changes I've made in the "What?" section above.
• I have performed a self-review of my changes.
• I have run the npm start command locally and verified that the changes look good.

• I have made my changes in the docs/sources/next folder of the documentation.

Related PR(s)/Issue(s)

[ppcano]

@heitortsergent, If we want to have a dedicated page for the release note, then, I think we should port at least the latest 6 release notes.

[heitortsergent]

@ppcano 👍. I updated the PR to include the last six release notes, would you mind taking another look? 🙇

[ppcano]

@heitortsergent added a commit to sort the list.

For SEO, it may be a good idea to set the canonical attribute to the release note page on GitHub. I don't know if the docs support setting the canonical metatag.