Rollup merge of rust-lang#151274 - count_zeros_note, r=jhpratt

Include a link to `count_ones` in the docs for `uN::count_zeros` [docs only]

I did not update `iN` because `count_zeros` is reasonable for *negative* numbers.

Rendered:
<img width="1188" height="524" alt="image" src="https://github.com/user-attachments/assets/80ebf53c-3cde-4230-b436-d2148b07d4c8" />
<img width="1186" height="517" alt="image" src="https://github.com/user-attachments/assets/544d2ff4-ee35-44f7-8d50-65fc5f0ff3c9" />

Author: jhpratt

library/core/src/num/uint_macros.rs

@@ -93,6 +93,28 @@ macro_rules! uint_impl {
         #[doc = concat!("let max = ", stringify!($SelfT),"::MAX;")]
         /// assert_eq!(max.count_zeros(), 0);
         /// ```
+        ///
+        /// This is heavily dependent on the width of the type, and thus
+        /// might give surprising results depending on type inference:
+        /// ```
+        /// # fn foo(_: u8) {}
+        /// # fn bar(_: u16) {}
+        /// let lucky = 7;
+        /// foo(lucky);
+        /// assert_eq!(lucky.count_zeros(), 5);
+        /// assert_eq!(lucky.count_ones(), 3);
+        ///
+        /// let lucky = 7;
+        /// bar(lucky);
+        /// assert_eq!(lucky.count_zeros(), 13);
+        /// assert_eq!(lucky.count_ones(), 3);
+        /// ```
+        /// You might want to use [`Self::count_ones`] instead, or emphasize
+        /// the type you're using in the call rather than method syntax:
+        /// ```
+        /// let small = 1;
+        #[doc = concat!("assert_eq!(", stringify!($SelfT), "::count_zeros(small), ", stringify!($BITS_MINUS_ONE) ,");")]
+        /// ```
         #[stable(feature = "rust1", since = "1.0.0")]
         #[rustc_const_stable(feature = "const_math", since = "1.32.0")]
         #[must_use = "this returns the result of the operation, \