Add support for indices.stats

[Xtansia]

Description

Describe what this change achieves.

Issues Resolved

Fixes #716

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[dblock]

Leaving open, take a look at integration tests.

[opensearch-trigger-bot]

The backport to 1.x failed:

The process '/usr/bin/git' failed with exit code 1

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.x 1.x
# Navigate to the new working tree
cd .worktrees/backport-1.x
# Create a new branch
git switch --create backport/backport-753-to-1.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 43ba0de9099c3bce9eeb95344c46db666af9c434
# Push it to GitHub
git push --set-upstream origin backport/backport-753-to-1.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.x

Then, create a pull request where the base branch is 1.x and the compare/head branch is backport/backport-753-to-1.x.