Make replica placement range and table aware

The current replica placement algorithm uses the power of two choices algorithm. This algorithm randomly selects tservers and places the replica on the tserver with less replicas. This can lead to potential hotspotting as it doesn't discriminate by range or table so many tablets from the same range/table can be disproportionally distributed.

With this new feature, the replicas will be placed in a way that the tablets per range will be equally distributed amongst the available tservers. If multiple tservers have the same amount of replicas per range, then the tserver with less replicas for that table will be selected. If multiple tservers have the same amount of replicas for that table, the tserver with less total replicas will be chosen.