Use EVM to replace eth_call for pure functions

[xianny]

Expected Behavior

Generated contract wrappers should reroute calls to pure Solidity functions to a native EVM implementation.

Current Behavior

Generated wrappers make an eth_call for every Solidity function called

Possible Solution

In abi-gen-templates, check if stateMutability === pure for each function and then reroute to an EVM if so.

[stale]

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