Add agent slippage controls

[dpaiton]

Agents should be able to specify a maximum loss they will accept due to slippage or higher-priority trades on the same block. If the criteria is not met, then the transaction reverts.

[dpaiton]

Only need to worry about slippage control when bots are executing on smart contracts -- so add the config parameter and pipe it to the contract call

[dpaiton]

addressed by #740