Update the sharding example to using a new 'tt' application layout #438
Description
As a part of tarantool/doc#3501, we need to start recommending our users to utilize tt instead of the tarantoolctl utility. This requires updating the sharding sample stored in the example directory. Currently, the example uses tarantoolctl commands for running and stopping instances (see Makefile). The example might also be updated to a new application layout.