…_field, r=Nilstrieb

 Explanation that fields are being used when deriving `(Partial)Ord` on enums

When deriving `std::cmp::Ord` or `std::cmp::PartialOrd` on enums, their fields are compared if the variants are equal.
This means that the last assertion in the following snipped panics.
```rust
use std::cmp::{PartialEq, Eq, PartialOrd, Ord};

#[derive(PartialEq, Eq, PartialOrd, Ord)]
enum Sizes {
    Small(usize),
    Big(usize),
}

fn main() {
    let a = Sizes::Big(3);
    let b = Sizes::Big(5);
    let c = Sizes::Small(10);
    assert!( c < a);
    assert_eq!(a, c);
}
```

This is more often expected behavior than not, and can be easily circumvented, as discussed in [this thread](https://users.rust-lang.org/t/how-to-sort-enum-variants/52291/4).
But it is addressed nowhere in the documentation, yet.
So I stumbled across this, as I personally did not expect fields being used in `PartialOrd`.
I added the explanation to the documentation.

Rollup of 12 pull requests

Successful merges:

 - rust-lang#118639 (Undeprecate lint `unstable_features` and make use of it in the compiler)
 - rust-lang#118714 ( Explanation that fields are being used when deriving `(Partial)Ord` on enums)
 - rust-lang#119801 (Fix deallocation with wrong allocator in (A)Rc::from_box_in)
 - rust-lang#119948 (Make `unsafe_op_in_unsafe_fn` migrated in edition 2024)
 - rust-lang#119999 (remote-test: use u64 to represent file size)
 - rust-lang#120058 (bootstrap: improvements for compiler builds)
 - rust-lang#120160 (Manually implement derived `NonZero` traits.)
 - rust-lang#120177 (Remove duplicate dependencies for rustc)
 - rust-lang#120185 (coverage: Don't instrument `#[automatically_derived]` functions)
 - rust-lang#120194 (Shorten `#[must_use]` Diagnostic Message for `Option::is_none`)
 - rust-lang#120200 (Correct the anchor of an URL in an error message)
 - rust-lang#120203 (Replace `#!/bin/bash` with `#!/usr/bin/env bash` in rust-installer tests)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup merge of rust-lang#118714 - The-Ludwig:explain_ord_derive_enum_field, r=Nilstrieb

 Explanation that fields are being used when deriving `(Partial)Ord` on enums

When deriving `std::cmp::Ord` or `std::cmp::PartialOrd` on enums, their fields are compared if the variants are equal.
This means that the last assertion in the following snipped panics.
```rust
use std::cmp::{PartialEq, Eq, PartialOrd, Ord};

#[derive(PartialEq, Eq, PartialOrd, Ord)]
enum Sizes {
    Small(usize),
    Big(usize),
}

fn main() {
    let a = Sizes::Big(3);
    let b = Sizes::Big(5);
    let c = Sizes::Small(10);
    assert!( c < a);
    assert_eq!(a, c);
}
```

This is more often expected behavior than not, and can be easily circumvented, as discussed in [this thread](https://users.rust-lang.org/t/how-to-sort-enum-variants/52291/4).
But it is addressed nowhere in the documentation, yet.
So I stumbled across this, as I personally did not expect fields being used in `PartialOrd`.
I added the explanation to the documentation.