feat: Update method signature of int_from_ascii

[ajtribick]

• Tracking issue: Tracking Issue for int_from_ascii #134821

Following discussion on Zulip it appears the preference is to change the API for this feature as follows:

// core::num

impl X {
    pub const fn from_ascii_bytes<T>(src: T) -> Result<X, ParseIntError>
    where
        T: [const] AsRef<[u8]> + [const] core::marker::Destruct;

    pub const fn from_ascii_bytes_radix<T>(src: T, radix: u32) -> Result<X, ParseIntError>
    where
        T: [const] AsRef<[u8]> + [const] core::marker::Destruct;
}

and similarly for NonZero<X>.

Reasons behind the change:

• Future-proof the naming convention for future string-like types
• Support the upcoming ByteStr/ByteString types: Tracking Issue for ByteStr/ByteString #134915

This pull request applies this change. The const-ness of these functions is now feature gated behind #143773

[rustbot]

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[Mark-Simulacrum]

@bors r+

[rust-bors]

📌 Commit 0bd28ea has been approved by Mark-Simulacrum

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 100. This pull request will be tested once the tree is reopened.

Reason for tree closure: spurious failures