Add release notes for 2.12.0

[RyanL1997]

Description

Add release notes for 2.12.0

Issues Resolved

• Relate [RELEASE] Release version 2.12.0 #1104

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e560f3a) 55.00% compared to head (f567f45) 55.00%.
Report is 1 commits behind head on 2.12.

Additional details and impacted files

@@           Coverage Diff           @@
##             2.12    #1430   +/-   ##
=======================================
  Coverage   55.00%   55.00%           
=======================================
  Files         315      315           
  Lines       11178    11178           
  Branches     2992     2992           
=======================================
  Hits         6149     6149           
  Misses       4978     4978           
  Partials       51       51           

Flag	Coverage Δ
dashboards-observability	55.00% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[opensearch-trigger-bot]

The backport to 2.12 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/dashboards-observability/backport-2.12 2.12
# Navigate to the new working tree
pushd ../.worktrees/dashboards-observability/backport-2.12
# Create a new branch
git switch --create backport/backport-1430-to-2.12
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 b15346dd4e13b707824a7c1abdd47bf1c13b93a4
# Push it to GitHub
git push --set-upstream origin backport/backport-1430-to-2.12
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/dashboards-observability/backport-2.12

Then, create a pull request where the base branch is 2.12 and the compare/head branch is backport/backport-1430-to-2.12.