feat: arbitrary call

[antoncoding]

Rationale

it would be nice for the engine to support arbitrary call to a interface as one of the actions. So we can do things like mint and fill order in a single transaction without using a wrapper

Concern

This mythology is well-explored with opyn, dydx's code base, but also might introduce an attack factor for things like flashloan to happen. (do arbitrary call -> transfer accounts to another address before margin checks -> skip check). While ensuring this is relatively easy because full collat engine have simple entry point, extra caution must be taken