Add leading/trailing ones and zero count instructions (part 1)

[Fumuran]

This PR adds 5 new instructions:

• u32clz: count leading zeros of the u32 value. [n, ...] -> [clz, ...]
• u32ctz: count trailing zeros of the u32 value. [n, ...] -> [ctz, ...]
• u32clo: count leading ones of the u32 value. [n, ...] -> [clo, ...]
• u32cto: count trailing ones of the u32 value. [n, ...] -> [cto, ...]
• ilog2: calculate the base 2 logarithm of the top stack element, rounded down. [n, ...] -> [ilog2, ...]

All these instructions work with help of the advice provider.
This PR partially implements features mentioned in #1133 issue. In the next PR corresponding procedures will be implemented in the std::math::u64 module.

[bobbinth]

Thank you! Not a review yet - but I left a couple of nits inline which also apply to many other places.

[plafer]

Looks good! Left some suggestions and questions

[plafer]

I would change as u32 to try_into()?, effectively returning a meaningful error to the user right away as opposed to silently computing the number of leading zeros on a different number (whatever it wrapped down to).

Same comment applies to other advice injectors

[bobbinth]

I agree, but also I think we should rename the injectors to make it clear that these injectors are only for u32 values. The names could be: U32Clz, U32Ctz etc.

Though, one issue with this naming is that it is not consistent with DivU64. So, we either rename it to U64Div or use ClzU32 etc. I slightly prefer the U64Div etc. approach.

[plafer]

This logic is copy/pasted across the other functions. There are a few ways to extract that logic to make it more generally useful, but one option would be something like

pub(crate) fn push_trailing_zeros<S: ProcessState, A: AdviceProvider>(
    advice_provider: &mut A,
    process: &S,
) -> Result<HostResponse, ExecutionError> {
    push_transformed_stack_top(|stack_top| {
        let stack_top = stack_top.as_int() as u32;
        Felt::new(stack_top.trailing_zeros().into())
    })
}

fn push_transformed_stack_top(f: impl FnOnce(Felt) -> Felt) -> Result<HostResponse, ExecutionError> {
    let stack_top = process.get_stack_item(0);
    let transformed_stack_top = f(stack_top);
    advice_provider.push_stack(AdviceSource::Value(transformed_stack_top))?;
    Ok(HostResponse::None)
}

If we also apply the previous comment about returning an error instead of using as u32, we make the closure return a Result<Felt, ExecutionError> instead of Felt

[plafer]

LGTM, great work!

The CI failure is due to a recent update to nightly Rust clippy; it's probably best to fix in another PR

[hackaugusto]

I think there is a bug in the ilog2 check. (Edit: ahhhh, where is my comment? Adding it 😬 )

The issue I raised was a non-problem

[bobbinth]

Looks good! Thank you!