Let the max_gas() function in BuiltinActor's take argument(s)

[ekovalev]

In the modification made to the BuiltinActor trait (#4345), the new max_gas() function - a counterpart of the "weight()" function for pallets extrinsics, does not accept any arguments, so it can only report a single maximum gas needed for any message processing, regardless of the concrete payload.
This can backfire in cases when a builtin actor has very different execution paths depending on the payload, when we would have to prohibit actual light and fast handle based on a mere possibility it could have been a heavy and slow one.

To account for this we might want to let max_gas take some complexity arguments; it could be a "complexity" argument (similarly to what we have for extrinsics' weight functions) or some small fraction of the payload (the first byte or something) that would provide a clue about the actual execution path inside the handle etc.

That we can have more accurate estimation of the expected gas budged based on the actual message payload.