Use EEI methods in opFns

[s1na]

As discussed (#455, #441), this PR introduces an interface exposed to the EVM for interacting with its environment. It closely resembles (and was inspired by) the ewasm EEI spec, the main difference being how input and output data is handled (ewasm requires buffers to be exchanged via memory).

The biggest changes are in how CALLs and CREATEs are handled. Although the logic is the same, there are now multiple functions for handling each specific type (as opposed to makeCall which handled everything).

The list of selfdestructed contracts is also kept now in Interpreter as part of a txRunState instead of being passed around with every message (added to runCode for backwards compatibility).

(To be merged into #479)

[coveralls]

Coverage decreased (-0.4%) to 94.083% when pulling 52dab72 on refactor/eei into 4678325 on v4.

[holgerd77]

👍 Cool! Will look into this shortly.

[holgerd77]

I am through, again, not line-by-line but checking overall consistency. I find this PR fantastic, since it brings so much clarity to the core logic here, would actually give this a go. Great work Sina! 😊