[9.2] (backport #18446) Release notes for 9.1.8

[mergify]

Since docs are built from 9.2, backport the 9.1.8 release notes to this branch.

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This is an automatic backport of pull request #18446 done by [Mergify](https://mergify.com). (with some handmande conflict resolutions)

[mergify]

Cherry-pick of e4d32ac has failed:

On branch mergify/bp/9.2/pr-18446
Your branch is up to date with 'origin/9.2'.

You are currently cherry-picking commit e4d32ac4.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   docs/release-notes/index.md

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[github-actions]

🤖 GitHub comments

Just comment with:

• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)
• /run exhaustive tests : Run the exhaustive tests Buildkite pipeline.

[github-actions]

🔍 Preview links for changed docs

• docs/release-notes/index.md

[mergify]

This pull request has not been merged yet. Could you please review and merge it @? 🙏