Reduce number of scanned index entries on chunk migration commit

In SERVER-64148 we changed the ShardingCatalogClient::commitChunkMigration implementation to make it compatible with the new moveRange command. This command can move a sub range of an existing chunk.

In particular we changed the query to find the chunk being moved. Since the new query is not sorted and use a limit of 2 it will need to scan all the index entries with min value less than the minimum shard key of the range to migrate.