feat: add num::traits::ops::OverflowingAdd trait

[enitrat]

Adds a trait for overflowing add operations.

This is particularly useful when writing generic implementations that require wrapping or overflowing operations.
Once discussed and approved, I will also work on OverflowingSub, OverflowingMul traits, and later on on Wrapping traits.

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This change is 

[orizi]

Reviewed 5 of 5 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @enitrat)

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corelib/src/num/traits/ops/overflowing.cairo line 3 at r1 (raw file):

/// Performs addition with a flag for overflow.
pub trait OverflowingAdd<T> {
    /// Returns a tuple of the sum along with a boolean indicating whether an arithmetic overflow would occur.

Suggestion:

    /// Returns a tuple of the sum along with a boolean indicating whether an arithmetic overflow
    /// would occur.

[orizi]

Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @enitrat)

a discussion (no related file):
@gilbens-starkware for 2nd eye.

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[gilbens-starkware]

Reviewed 1 of 5 files at r1, all commit messages.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @enitrat)

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corelib/src/integer.cairo line 2750 at r1 (raw file):

// OverflowingAdd implementations

impl U8OverflowingAdd of core::num::traits::OverflowingAdd<u8> {

Suggestion:

// OverflowingAdd implementations
impl U8OverflowingAdd of core::num::traits::OverflowingAdd<u8> {

[enitrat]

Reviewable status: 3 of 5 files reviewed, 2 unresolved discussions (waiting on @orizi)

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corelib/src/num/traits/ops/overflowing.cairo line 3 at r1 (raw file):

/// Performs addition with a flag for overflow.
pub trait OverflowingAdd<T> {
    /// Returns a tuple of the sum along with a boolean indicating whether an arithmetic overflow would occur.

Done.

[orizi]

Reviewed 1 of 2 files at r2, 1 of 1 files at r3, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @enitrat)

[orizi]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @enitrat)

[gilbens-starkware]

Reviewed 2 of 5 files at r1, 1 of 2 files at r2, 1 of 1 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @enitrat)