change Debug format for fields

[plafer]

Implements Debug by hand for the base fields such that it outputs a human-readable integer.

The current behavior makes the fields unintuitive when debugging Vec<BaseElement>. Specifically, Vec doesn't implement Display, so we're forced to use the Debug output:

let v: Vec<BaseElement> = vec![BaseElement::from(1u64)];

println!("{v:?}");

// current output: [ BaseElement(<Montgomery form of 1>) ]
// new output: [ 1 ]

I believe most users will be confused by the current output, and would expect to read an integer (as I was).

[irakliyk]

Looks good! Thank you!

[irakliyk]

winter-math v0.7.1, which includes this change, has also now been published to crates.io.