Optimization for bool's PartialOrd impl

[ChayimFriedman2]

#66780 suggested an optimization for impl Ord for bool, and it was implemented in #66881.

However, for some reason, impl PartialOrd for bool was not optimized the same way:

rust/library/core/src/cmp.rs

Lines 1286 to 1300 in 1f7762b

	impl Ord for bool {
	#[inline]
	fn cmp(&self, other: &bool) -> Ordering {
	// Casting to i8's and converting the difference to an Ordering generates
	// more optimal assembly.
	// See <https://github.com/rust-lang/rust/issues/66780> for more info.
	match (*self as i8) - (*other as i8) {
	-1 => Less,
	0 => Equal,
	1 => Greater,
	// SAFETY: bool as i8 returns 0 or 1, so the difference can't be anything else
	_ => unsafe { unreachable_unchecked() },
	}
	}
	}

rust/library/core/src/cmp.rs

Lines 1236 to 1241 in 1f7762b

	impl PartialOrd for bool {
	#[inline]
	fn partial_cmp(&self, other: &bool) -> Option<Ordering> {
	(*self as u8).partial_cmp(&(*other as u8))
	}
	}

It can be implemented in terms of Ord:

    impl PartialOrd for bool {
        #[inline]
        fn partial_cmp(&self, other: &bool) -> Option<Ordering> {
            Some(self.cmp(other))
        }
    }

Is this deliberate or just something that no-one noticed?

[camelid]

By the way, you don't need to open an issue if you're about to open a PR. Just include what you would put in the issue in the PR!