Rollup merge of rust-lang#99692 - RalfJung:too-far, r=oli-obk

interpret, ptr_offset_from: refactor and test too-far-apart check

We didn't have any tests for the "too far apart" message, and indeed that check mostly relied on the in-bounds check and was otherwise probably not entirely correct... so I rewrote that check, and it is before the in-bounds check so we can test it separately.

Author: Dylan-DPC

core/src/ptr/const_ptr.rs

@@ -730,7 +730,7 @@ impl<T: ?Sized> *const T {
     /// }
     ///
     /// // This would be incorrect, as the pointers are not correctly ordered:
-    /// // ptr1.offset_from(ptr2)
+    /// // ptr1.sub_ptr(ptr2)
     /// ```
     #[unstable(feature = "ptr_sub_ptr", issue = "95892")]
     #[rustc_const_unstable(feature = "const_ptr_sub_ptr", issue = "95892")]