Debugger Refactor #1: fuzz single

[iFrostizz]

First part of #5547 breaking into smaller chunks.
This PR refactors the fuzz function in order to have access to a more granular, single-step, function called single_fuzz.
It will let us in the context of the debugger to be able to run again the fuzzer on the last relevant (either a counter-example, or the first case, see the current imeplemtnation of the debugger launching https://github.com/foundry-rs/foundry/blob/master/crates/forge/bin/cmd/test/mod.rs#L209-L213 with this time debug traces (they are expensive, especially when fuzzed).

[Evalir]

Nice! Loving how small this is. Some comments on docs and other things

wondering if it's possible to get a PR description on what exactly this is deduping? It's pretty clear if you read the code, but just for future reference

Also wondering, are these split PRs safe to be merged in any order or should we hold off?

[iFrostizz]

Thanks @Evalir ! Adding a desc soon!
I'll streamline the PRs as they go to build https://github.com/foundry-rs/foundry/pull/5547/files with a reasonable amount of changes, would be great to merge them in order to avoid duplicate work.

[iFrostizz]

@Evalir @mattsse What's up with this one ?

[mattsse]

ty for breaking this up into smaller chunks!

some nits, otherwise lgtm

[Evalir]

@iFrostizz sorry for the long review time—we've been setting up for travel and traveling over the past week so it's taken a tad more time to review things—let's get this in ASAP

[Evalir]

sweet, looks good. just a smol nit on docs

will defer to @mattsse for final approve / merge

[iFrostizz]

@Evalir all good, and hope that you're all having fun there!
Thanks for the review :)

[iFrostizz]

Could we get rid of this use of RefCell ? https://github.com/foundry-rs/foundry/blob/master/crates/evm/src/fuzz/mod.rs#L67-L80
Also, in a further PR we could get rid of the FuzzCase struct

[Evalir]

@iFrostizz if it's not needed anymore, then sure!

[iFrostizz]

@Evalir could that be preferably done after the debugger refactor ?

[Evalir]

yep sounds good!

@mattsse friendly ping

[Evalir]

aight sweet, sorry for taking so long with this one—let's send it and keep iterating

[iFrostizz]

thanks @Evalir !
next one coming soon, prob gonna be the last one, sorry I couldn't cut less. But noticed that some code moves were unnecessary for that task, so it should be reduced to ~500 lines i hope!