Enable cross-cluster monitor cluster setting

[goyamegh]

Issue #, if available:

Description of changes:
Enable cross-cluster monitor cluster setting

CheckList:

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[AWSHurneyt]

Approving assuming CI passes.

[AWSHurneyt]

Backporting back to v2.14 as the feature received GA launch approval after 2.13 open source release.

[AWSHurneyt]

The failing test is org.opensearch.alerting.transport.GetRemoteIndexesActionIT > test with remote monitoring disabled.
https://github.com/opensearch-project/alerting/actions/runs/9999216318/job/27639794066?pr=1612#step:5:334

That test suite has a helper function which should be toggling the feature on/off; but it looks like it's failing to disable to feature before the start of that test. Troubleshooting that test.

[AWSHurneyt]

The failing test is org.opensearch.alerting.transport.GetRemoteIndexesActionIT > test with remote monitoring disabled. https://github.com/opensearch-project/alerting/actions/runs/9999216318/job/27639794066?pr=1612#step:5:334

That test suite has a helper function which should be toggling the feature on/off; but it looks like it's failing to disable to feature before the start of that test. Troubleshooting that test.

Fixed in commit 478eb46

[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/alerting/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/alerting/backport-2.x
# Create a new branch
git switch --create backport-1612-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 7c69e091c81f585ebf5a1e96bfab862dab990191
# Push it to GitHub
git push --set-upstream origin backport-1612-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/alerting/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport-1612-to-2.x.

[opensearch-trigger-bot]

The backport to 2.14 failed:

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

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/alerting/backport-2.14 2.14
# Navigate to the new working tree
pushd ../.worktrees/alerting/backport-2.14
# Create a new branch
git switch --create backport-1612-to-2.14
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 7c69e091c81f585ebf5a1e96bfab862dab990191
# Push it to GitHub
git push --set-upstream origin backport-1612-to-2.14
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/alerting/backport-2.14

Then, create a pull request where the base branch is 2.14 and the compare/head branch is backport-1612-to-2.14.

[opensearch-trigger-bot]

The backport to 2.15 failed:

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

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/alerting/backport-2.15 2.15
# Navigate to the new working tree
pushd ../.worktrees/alerting/backport-2.15
# Create a new branch
git switch --create backport-1612-to-2.15
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 7c69e091c81f585ebf5a1e96bfab862dab990191
# Push it to GitHub
git push --set-upstream origin backport-1612-to-2.15
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/alerting/backport-2.15

Then, create a pull request where the base branch is 2.15 and the compare/head branch is backport-1612-to-2.15.