Detect transaction with larger gas usage

[gustavo-grieco]

Once #75 is merged, we should generalize the code to allow medusa to show the most expensive transaction in terms of gas used.

[Xenomega]

Idea: The fuzzer_metrics.go file is pretty simple/sad. We could revamp it to track this and other statistics there. And leave room for arbitrary statistics users might have in their tests.

[gustavo-grieco]

There is a draft for this feature in #165

[anishnaik]

@ggrieco-tob putting this on hold for now. The PR lgtm but de-prioritizing this for a future milestone. Given the large refactor that will happen with #51, I think we should wait on this. Lmk if you disagree.

[anishnaik]

Removing this from "on hold" to low priority. We should try to close this out and review the PR in the next few milestones.