This is the interface for storage miners to withdaw stakings. You must be in exied state to withdaw them.
// MinerWithdraw withdraws all staking
//
// Return:
// - string: block hash
// - error: error message
//
// Note:
// - must be an exited miner to withdraw
// - wait a day to withdraw after pre-exit
func (c *ChainClient) MinerWithdraw() (string, error)
