Once the cost tracking implementation is complete, we should add some tests for it to ensure parity with the interpreter.

Our existing test infrastructure should make adding a comparison between the interpreter and the WebAssembly runtime's accounting of costs not too difficult. By modifying TestEnvironment::init_contract_with_snippet to use both the interpreter's and the runtime's cost tracking, all the tests that rely on crosschecking the results of executing a contract will now also check the cost tracking code.