Add render search template as a cluster permission

[cwperks]

Description

Companion PRs in core:

• Create separate transport action for render search template action OpenSearch#11170
• Add additional handling in SearchTemplateRequest when simulate is set to true OpenSearch#11591

This PR adds render search template as a cluster perm so that its separately permissioned from a SearchTemplateRequest which needs a set of indices to authorize the request. The companion PR in core separates the transport actions that handle search template request and render search template request so that they can be authorized separately.

I am opening this in Draft until the core PR is merged because this PR depends on the core PR.

• Category (Enhancement, New feature, Bug fix, Test fix, Refactoring, Maintenance, Documentation)

Bug fix

Issues Resolved

• [BUG] POST /_render/template results in a NullPointerException when security plugin is enabled #3672

Check List

• New functionality includes testing
• New functionality has been documented
• 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.

[DarshitChanpura]

@cwperks are you still working on this?

[cwperks]

@DarshitChanpura yes, the companion PR has not yet been reviewed in core.

[cwperks]

The companion core PR was merged, this is ready for review now.

[peternied]

@cwperks Can you get the CI green? Happy to look afterward

[cwperks]

@peternied There's another change in core that needs to be reviewed for the CI in this PR to turn green: opensearch-project/OpenSearch#11591

[cwperks]

@peternied The CI checks are passing now after the core PRs were merged. Thank you for helping out!

I'll also file a PR in the security-dashboards-plugin repo to add the render search template transport action name to the cluster permission dropdown.

[opensearch-trigger-bot]

The backport to 2.x 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/security/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/security/backport-2.x
# Create a new branch
git switch --create backport/backport-3689-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 cc577101240a65b5932ebaf9193f3a8968ecba64
# Push it to GitHub
git push --set-upstream origin backport/backport-3689-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/security/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-3689-to-2.x.