Update the ShardSplitCommands to use the TenantId class

Change the Shard Split Commands (commitShardSplit) to use a vector<tenant_id> instead of vector<string>. Part of the change could include a couple helper methods to convert a vector<tenant_id> to a vector<string> (StringData) and vector<string> to a vector<tenant_id>. We should also change the javascript code to support the change in the parameter. Also making necessary changes at the shard_split_test api. We should also make changes to the shard split passthrough to also support the proper object if necessary.