perf(cheatcodes): outline cold paths in inspector step

[DaniPopes]

Outlining (and marking as cold) the Inspector::step cold paths in the cheatcodes inspector (so gas metering, mapping etc) makes the function trivial to inline as it becomes just a few checks, as well as way more cache-friendly as it won't have to jump around thousands of bytes on the common case where all or most of the conditions are false.

Overall this makes forge 5% to 20% faster depending on the workload

[DaniPopes]

The diff here is horrendous, basically the inner block of if let X = Y { ... } in fn step were moved to the bottom of the file in their own impl block, plus some refactors

[mattsse]

lgtm, but this impacts #8123

merging this first is the right way to do this.
depending on how big the conflicts are, perhaps you could then take a look at resolving them in #8123 ?