[Backport 1.x] Update MAINTAINERS.md

[ananzh]

Description

Coming from opensearch-project/.github#121, updated MAINTAINERS.md to match opensearch-project recommended format. Also modify this file to include all the missing updates.

Since we won't include this in release, ignore CHANGELOG.

Check List

• All tests pass
  • yarn test:jest
  • yarn test:jest_integration
  • yarn test:ftr
• New functionality includes testing.
• New functionality has been documented.
• Update CHANGELOG.md
• Commits are signed per the DCO using --signoff

[opensearch-trigger-bot]

The backport to 1.3 failed:

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

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/backport-1.3 1.3
# Navigate to the new working tree
pushd ../.worktrees/backport-1.3
# Create a new branch
git switch --create backport/backport-3338-to-1.3
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 a9833979b822791e6231ec17864f17d2bfc22d72
# Push it to GitHub
git push --set-upstream origin backport/backport-3338-to-1.3
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-1.3

Then, create a pull request where the base branch is 1.3 and the compare/head branch is backport/backport-3338-to-1.3.