In this ticket, we will change high level interface function of sharding code to take in DatabaseName instead of string db.

• the function is a high level interface function
• if we already have nss or DatabaseName object in its call sites, we need to change it.
• Otherwise, if this function is called from non-shard code, we also need to change it.
  for example, the `ScopedBaseDDLLock` and `executeCommandAgainstDatabasePrimary` function should be changed.

We will not change the low level functions of sharding code (eg, `logEnableSharding`) in this ticket.