Add flat_skew setting to node overload decider

[imRishN]

Description

This Pull Request fixes the issue of unassigned shards when cluster fails to rebalance itself after a partial zonal outage recovery by adding a dynamic setting called flat_slew to the load_awareness decider. More details on the bug can be found on the issue

Issues Resolved

#3497

Check List

• New functionality includes testing.
• All tests pass
• New functionality has been documented.
• New functionality has javadoc 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.

[opensearch-ci-bot]

❌   Gradle Check failure 4f82d02cff1ec96e219bd13a5ef20cd9963d25b0
Log 5908

Reports 5908

[Bukhtawar]

Can you please fix the spotless checks

[opensearch-ci-bot]

❌   Gradle Check failure d8de24020207f0033fd2b7e51e8f1afa5521ba9b
Log 5916

Reports 5916

[Bukhtawar]

Failed test #3565

[Bukhtawar]

start gradle check

[opensearch-ci-bot]

❌   Gradle Check failure d8de24020207f0033fd2b7e51e8f1afa5521ba9b
Log 5917

Reports 5917

[opensearch-ci-bot]

❌   Gradle Check failure 5aca9f4b5d19e82ec50c6406d025a9ac1577c548
Log 5918

Reports 5918

[opensearch-ci-bot]

❌   Gradle Check failure ec74abac375a9f548123dda70202833b2670bcde
Log 5919

Reports 5919

[Bukhtawar]

start gradle check

[opensearch-ci-bot]

❌   Gradle Check failure ec74abac375a9f548123dda70202833b2670bcde
Log 5920

Reports 5920

[opensearch-ci-bot]

✅   Gradle Check success 5b8f65d
Log 5963

Reports 5963

[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-3563-to-1.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 836a9c4910f5eb4e7fcaca5573bd3bf47073d416
# Push it to GitHub
git push --set-upstream origin backport/backport-3563-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-3563-to-1.x.