sharding: create a syncer and a simulator package Former-commit-id: b392885510ba5a96e61278cbbe2c0ec6f9722ee8 [formerly 3a435eaf6805d02beae55656f155b2c3a66ee663] Former-commit-id: 0f6f3f2053ae77711e2072848b727b0dc9b92276