[Backport 3.5] Add 3.5 Release Notes

[opensearch-trigger-bot]

Backport f83d89d from #5092.

[coderabbitai]

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch backport/backport-5092-to-3.5

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[opensearch-trigger-bot]

The backport to 3.5 failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/sql/backport-3.5 3.5
# Navigate to the new working tree
pushd ../.worktrees/sql/backport-3.5
# Create a new branch
git switch --create backport/backport-5094-to-3.5
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 d99377a0a55ec68b69c4a0721de31fff12f45cea
# Push it to GitHub
git push --set-upstream origin backport/backport-5094-to-3.5
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/sql/backport-3.5

Then, create a pull request where the base branch is 3.5 and the compare/head branch is backport/backport-5094-to-3.5.