Benchmarking CLI improvements

A few small things that would be great to improve in benchmarking CLI:

1. We should use `structop` instead of `clap` as thats what we use for all other CLIs (e.g., [here](https://github.com/0xPolygonMiden/miden-vm/blob/main/miden/src/main.rs#L13)).
2. We should keep CLI parameters as consistent as possible across different CLIs (e.g., for how we specify security, number of outputs etc.). See example [here](https://github.com/0xPolygonMiden/miden-vm/blob/main/miden/src/cli/prove.rs#L11).
3. Let's change the executable file name to something like `miden-bench` (`miden-benchmarking-cli` is way too long).
4. `miden::prove()` also includes execution time, I believe. So, to make things more clear, we should probably label it as "Execution + proving time" or something like that.
5. Would also be great to print out proof size.

Look at the benchmarking CLI code in the examples repository, likely in a `benches` or `cli` directory. Compare with the main Miden VM CLI using structopt (e.g., `miden/src/main.rs` and `miden/src/cli/prove.rs`). Update the argument parsing, rename the executable in Cargo.toml, adjust timing labels in output, and add proof size reporting. Run the benchmarks to verify changes.

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