Add circuit flamegraphs to openvm-prof

[jonathanpwang]

Move ci/scripts/metrics_unify/flamegraph.py to openvm-prof (in a flamegraph.rs file)
I think we could directly use inferno without a subprocess call to cargo-flamegraph.

[alv-around]

What about samply, (flamegrpah.rs recomend it in their README.md). I tested on the sdk you just need define a [profile.profiling] and works out-of-box.

[jonathanpwang]

What about samply, (flamegrpah.rs recomend it in their README.md). I tested on the sdk you just need define a [profile.profiling] and works out-of-box.

Here I am referring to this script which is for circuit flamegraphs where we emit custom metrics (similar to linux perf but specific to VM / STARKs). The python script parses them into a format compatible with flamegraph. Indeed you could also output a profile.json that could be given to samply -- I haven't looked into this but it would be cool.