Decimal - add checked_div_euclid

[ueco-jb]

part of #1186

[webmaster128]

Okay, it took me a bit to figure out what euclid division actually does. It seems to be relatively straight forward as long as no negative numbers are involved. I found https://www.probabilisticworld.com/euclidean-division-integer-division-with-remainders/ useful.

Looking at the Decimal implementation, it is possible to trigger unnecessary errors in the current implementation (fails with panicked at 'called Result::unwrap() on an Err value: Overflow'):

        // The regular division result (340282366920938463463.6) would be out of range.
        assert_eq!(
            dec("170141183460469231731.8")
                .checked_div_euclid(dec("0.5"))
                .unwrap(),
            dec("340282366920938463463")
        );

I suggest splitting the uint implementations and the decimal implementation in two PRs and try to find a better implementation for decimals.

[uint]

@webmaster128 Euclidean division seems to be defined as an operation between two integers. See here. Since we're dealing with decimals here, it doesn't seem applicable.

[webmaster128]

Ah, good point. Thanks for pointing that out! It is also not implemented for float types in Rust (https://doc.rust-lang.org/std/?search=checked_div_euclid).

[webmaster128]

Closing due to #1365 (comment). The int implementations are here: #1376