Add advanced fuzzer (#724)

[xgreenx]

PR currently blocked on https://github.com/FuelLabs/fuel-vm/issues/815

Closes https://github.com/FuelLabs/fuel-core/issues/1443 Related https://github.com/FuelLabs/fuel-vm/issues/718

The original PR. I moved the change to our codebase to see how CI works, plus it allows us to commit changes as well. Huge thanks to the @maxammann for finalizing the PR!

Edit (@netrome): I have done a few modifications on the original PR to make this ready to merge.

• Cleaned up unused code and clippy errors so the PR passes CI.
• Removed the outdated and broken grammar_aware fuzz target.
• Updated the README.md with instructions for how to generate a corpus, run the fuzzer, generate code coverage reports.
• Added an example initial corpus so people don't have to generate a corpus from scratch to run the fuzzer.
• Added the libafl and libfuzzer feature flags to toggle between the LibAFL and LibFuzzer fuzzers, without having to manually comment out dependencies, as the original PR required.
• Did an initial investigation of discovered crashes, and created https://github.com/FuelLabs/fuel-vm/issues/815 to further investigate and resolve this.

Before requesting review

• [x] I have reviewed the code myself
• [x] I have created follow-up issues caused by this PR and linked them here

[maxammann]

Sounds good, feel free to do the same with the others :) As I can not really commit to this PR I'm checking this off my todo for now.

I think the other PR is mainly failing because external PRs don't have access to secrets, which is good.

Both PRs need a cargo format.

[netrome]

I think we don't need to include example corpus in the fuel-vm repository. The CI action could do all steps to produce corpus.

@netrome The final goal what we try to achieve is to run this fuzzer on nightly bases. Do you plan not add action in this PR, or it follow up?

Fair enough, I'll remove the example corpus. I plan to follow up with the CI work in the ClusterFuzzLite PR.

[netrome]

LGTM!=) I can't approve since I created this PR initially=D

Nice, I'll approve in your place=)