This missing part of EVMC processing allows third-party EVMs to work.
It fixes EVMC result processing (at the top-level of calls, not nested calls)
to use the EVMC result object, instead of reading so much internal state of the
Nimbus `Computation` object.
It has been tested by calling [`evmone`](https://github.com/ethereum/evmone)
and getting useful results with tracing enabled (`showTxCalls = true`). It's
even able to run parts of the fixtures test suite.
There are other issues with account balances, etc that need to be worked on to
get the correct _final_ results, but the EVM execution is correct with this.
Signed-off-by: Jamie Lokier <jamie@shareable.org>
072934272b