[RW Separation] Add polling segment replication for search replicas

[mch2]

Description

Add segment replication polling for search replicas. This PR introduces segrep polling for search replicas at the existing refresh interval. If the feature flag is enabled an async task from IndexService will trigger replication.

Related Issues

Related #4577

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

❕ Gradle check result for aef15f9: UNSTABLE

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[github-actions]

✅ Gradle check result for c6ddf1b: SUCCESS

[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/OpenSearch/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.x
# Create a new branch
git switch --create backport/backport-15627-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 375c0bf1c9ac9ff7226d447bcd1dddfcedd856fc
# Push it to GitHub
git push --set-upstream origin backport/backport-15627-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-15627-to-2.x.

[opensearch-trigger-bot]

The backport to 2.17 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/OpenSearch/backport-2.17 2.17
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.17
# Create a new branch
git switch --create backport/backport-15627-to-2.17
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 375c0bf1c9ac9ff7226d447bcd1dddfcedd856fc
# Push it to GitHub
git push --set-upstream origin backport/backport-15627-to-2.17
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.17

Then, create a pull request where the base branch is 2.17 and the compare/head branch is backport/backport-15627-to-2.17.