[release-3.9]Update CHANGELOG entries for 3.9.0 release

[himani2411]

Description of changes

• Update CHANGELOG entries for 3.9.0 release

Tests

• Describe the automated and/or manual tests executed to validate the patch.
• Describe the added/modified tests.

References

• Link to impacted open issues.
• Link to related PRs in other packages (i.e. cookbook, node).
• Link to documentation useful to understand the changes.

Checklist

• Make sure you are pointing to the right branch.
• If you're creating a patch for a branch other than develop add the branch name as prefix in the PR title (e.g. [release-3.6]).
• Check all commits' messages are clear, describing what and why vs how.
• Make sure to have added unit tests or integration tests to cover the new/modified code.
• Check if documentation is impacted by this change.

Please review the guidelines for contributing and Pull Request Instructions.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.21%. Comparing base (99aca8a) to head (068e956).

Additional details and impacted files

@@             Coverage Diff              @@
##           release-3.9    #6159   +/-   ##
============================================
  Coverage        90.21%   90.21%           
============================================
  Files              181      181           
  Lines            15838    15838           
============================================
  Hits             14288    14288           
  Misses            1550     1550           

Flag	Coverage Δ
unittests	90.21% <ø> (ø)

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[hanwen-pcluste]

This is item is already in CHANGES