Feature

Add a new command under cargo risczero called benchmark that will be responsible to prove a predefined guest code (bench) and report timings on execution, proving and lifting steps.

Motivation

We have an internal way to show local proving timings by running the loop example.
Its usage is not well documented and there's not much visibility around it as well. By providing a specific command under cargo risczero we would allow users to quickly run a benchmark on computing time in their machines, without necessarily downloading and compiling from source.

Implementation

Leverage the already existing bench guest code, and the code on loop example in order to create a standalone command bench under cargo risczero

Related issues:
#1245