Handle pending create indexes in file rebalance for on-prem deployments

In Elixir, the pending indexes are built in back-ground after rebalance is done. This is not ideal as index build is resource intensive and can impact scan latencies.

Instead, the code should be updated to handle pending create indexes as a part of rebalance itself as DCP rebalance can happen along with shard rebalance. The current implementation should work out of the box.