[AUTO] Add release notes for 3.2.0

[opensearch-ci-bot]

Add release notes for 3.2.0

[gaiksaya]

Hi @prudhvigodithi and other maintainers,

This is the first time we are trying the automation to create release notes based on the changes/commits that went in since last release (3.1.0) which was on June 24, 2025.
Please review the PR and provide feedback. Please feel free to commit the changes in the PR branch.
More details on the workflow
cc: @rishabh6788

[prudhvigodithi]

This is amazing, reduces one manual work for the release owner. @gaiksaya after this PR was created I do see there are some new changes added to the changelog. Is there a way I can trigger the workflow again to get them updated ?

[rishabh6788]

@prudhvigodithi The workflow has updated the pr, please review.

[gaiksaya]

Please review and merge so as to avoid backport to branches @prudhvigodithi

[andrross]

@prudhvigodithi The changelog on main should have been cleared out in this commit. Once the 3.2 branch is created and the release process begins, the changelog on main must only contain information about commits not included in the 3.2 release.

#18989