feat: add warnings and specifically unused variable warnings

[stringhandler]

This PR adds warnings, taken originally from #232, by themselves, without the extra clutter of infix operators.

However, I did want to add an unused variable warning.

A particularly dangerous case is where the developer uses an add_N jet, but doesn't do anything with the carry, allowing silent overflows.

fn main() {
    let a: u8 = 250;
    let b: u8 = 255;

    let (carry, sum) :(bool, u8) = jet::add_8(a,b);
    // carry is not used. This will generate a warning.
    assert!(jet::eq_8(sum, 200));

}

With this PR the warning is added:

warning: Variable `carry` is bound but never used. Prefix the variable name with `_` to silence this warning.     
 --> .\debug\unused_variable_warning.simf:5:6
  |
5 |     let (carry, sum) :(bool, u8) = jet::add_8(a,b);
  |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: `.\debug\unused_variable_warning.simf` generated 1 warning
Program:
4jTYfQIQKE2H+CEChBhxqKNLQQgUH0mJsMgECwZtoIwCBNB+FggG4DhAHDg=
CMR:
9b79d61e50740f752cfaf42f5dbf95c918e6cba7c1d2d4de1a2b16a9fa00f6f7

I also added scripts to run all the examples to see if they still compile. If this bugs anyone, I'm happy to remove it.

[apoelstra]

utACK 7f35d30 -- but CI needs fixing.

This looks great! In a followup we will want to abstract out the color formatting stuff but it's fine for shell codes to be hardcoded for now. I also suspect that we could find a nicer way to thread warnings through the whole codebase than to have these tuples everywhere, but let's not let the perfect be the enemy of the good.