EVM: Remove duplicate testing frameworks

[Stebalien]

We have:

• Functions in evm/tests/utils.rs for constructing actors.
• A framework in evm/tests/env.rs that duplicates the same logic.

We should probably just switch to a framework as that'll make it easier to manage. But we also have to consider which approach will be easier.

[Stebalien]

Specifically, both of these files provide tools for:

• Deploying EVM smart contracts (init_construct_and_verify, TestEnv::deploy).
• Calling EVM smart contracts (invoke_contract, TestEnv::call).

We should standardize around one abstraction (likely the TestEnv one unless switching to it is too disruptive).