[polish] include information about client that created tenant migration donor in currOp

This is the currentOp output for a tenant migration donor:

The donorStartMigration command creates a POS instance that runs in the background in  a thread pool. Would it be useful to include information about the client of the donorStartMigration command? 

A proposed output: 

{

   desc: ...,

   client: ...,

   appName: ...,

   clientMetadata: ...,

   ...other fields from above...

}

bruce.lucas

esha.maharishi