Replica Placement could be slow for new collection creation with high amount of shards in a cluster with plenty of replicas

It's found in our cluster with hundreds of thousands of replicas that collection creation is slow when the new collection has thousands of shards.

In particular there are 4 mins+ computation time spent between the collection initial creation and the SliceMutator creating slice

With some profiling and metrics checking, it appears that during those 4 mins, almost all of the CPU time is spent in org.apache.solr.cluster.placement.plugins.OrderedNodePlacementPlugin$WeightedNode.getAllReplicasOnNode.

For each new shard, it invokes this method to compute the weight which iterates on all collection and shard, with creation of a new replica set. This computation is costly for our environment based on the profiler and CPU metrics.