Increase default replica count for system indices

[ohltyler]

To help minimize impact for multi-cluster nodes, we should increase the default replica count from 0-1 => 0-5.

Ref: https://github.com/opensearch-project/flow-framework/blob/main/src/main/java/org/opensearch/flowframework/indices/FlowFrameworkIndicesHandler.java#L85

[dbwiddis]

@ohltyler Is this ask still relevant? This PR has been lingering for 4 months now.

[ohltyler]

I would confirm with @amitgalitz , I remember he mentioned this could cause issues. Low priority.