Enable easy access to cycle count, segment count, and executor time stats from running dev-mode

[Cardosaum]

A feature is proposed to simplify the process for users to view cycle count, segment count, and executor time statistics when running in development mode. By setting RISC0_DEV_MODE=1 and RUST_LOG="<module>=debug", a clear log of executor stats should be enabled. This feature aims to enhance the user experience by providing an easier way to obtain statistics about the program running.

[SchmErik]

So what we discussed was to put something like this in the template:

risc0/examples/zkevm-demo/src/main.rs

Line 43 in 2a7e912

env_logger::init();

This uses env_logger but we might want tracing subscriber instead.

And then, add log::info!(...); in the executor somewhere in this function:

risc0/risc0/zkvm/src/host/server/exec/executor.rs

Line 256 in d1b7a5e

pub fn run_with_callback<F>(&mut self, callback: F) -> Result<Session, ExecutorError>