Fixup libafl_fuzzbench-based fuzzers

[addisoncrump]

Fixes #2019.

[addisoncrump]

This PR also restores the mruby bug benchmark. Potentially I could bring back other benchmarks for these fuzzers.

@DonggeLiu, would you think it appropriate to run a fuzzbench run for these fuzzers + a working symbolic fuzzer + baselines (AFL++ and libafl at least) against mruby? After #2028 lands.

[DonggeLiu]

Yep sure, I would love to see the results too. Thanks for doing this, @addisoncrump!

If you are interested in running them on more bug-based benchmarks, they (and their results) can be found on sbft23 branch and #2022. @Dammo3 kindly added some benchmarks recently.

Two minor things:

1. We conventionally append the commit ID after the directory name of bug-based benchmarks, e.g., https://github.com/google/fuzzbench/tree/master/benchmarks/bloaty_fuzz_target_52948c

2. How about changin the type to type: bug: https://github.com/google/fuzzbench/blob/782b36195db07990654d9a0f312ca409efea7fde/benchmarks/bloaty_fuzz_target_52948c/benchmark.yaml#L20

[renatahodovan]

@addisoncrump Thanks for working on this! Is it planned to merge it anytime soon?

[addisoncrump]

This is ready to be merged.