Stabilize const_ptr_offset_from.

Stabilization has been completed [here](rust-lang/rust#92980 (comment))
with a FCP.

Author: fee1-dead

core/src/intrinsics.rs

@@ -2013,11 +2013,11 @@ extern "rust-intrinsic" {
     pub fn nontemporal_store<T>(ptr: *mut T, val: T);
 
     /// See documentation of `<*const T>::offset_from` for details.
-    #[rustc_const_unstable(feature = "const_ptr_offset_from", issue = "92980")]
+    #[rustc_const_stable(feature = "const_ptr_offset_from", since = "1.65.0")]
     pub fn ptr_offset_from<T>(ptr: *const T, base: *const T) -> isize;
 
     /// See documentation of `<*const T>::sub_ptr` for details.
-    #[rustc_const_unstable(feature = "const_ptr_offset_from", issue = "92980")]
+    #[rustc_const_stable(feature = "const_ptr_offset_from", since = "1.65.0")]
     pub fn ptr_offset_from_unsigned<T>(ptr: *const T, base: *const T) -> usize;
 
     /// See documentation of `<*const T>::guaranteed_eq` for details.

core/src/lib.rs

@@ -130,7 +130,6 @@
 #![feature(const_replace)]
 #![feature(const_ptr_as_ref)]
 #![feature(const_ptr_is_null)]
-#![feature(const_ptr_offset_from)]
 #![feature(const_ptr_read)]
 #![feature(const_ptr_write)]
 #![feature(const_raw_ptr_comparison)]

core/src/ptr/const_ptr.rs

@@ -641,7 +641,7 @@ impl<T: ?Sized> *const T {
     /// }
     /// ```
     #[stable(feature = "ptr_offset_from", since = "1.47.0")]
-    #[rustc_const_unstable(feature = "const_ptr_offset_from", issue = "92980")]
+    #[rustc_const_stable(feature = "const_ptr_offset_from", since = "1.65.0")]
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn offset_from(self, origin: *const T) -> isize

core/src/ptr/mut_ptr.rs

@@ -824,7 +824,7 @@ impl<T: ?Sized> *mut T {
     /// }
     /// ```
     #[stable(feature = "ptr_offset_from", since = "1.47.0")]
-    #[rustc_const_unstable(feature = "const_ptr_offset_from", issue = "92980")]
+    #[rustc_const_stable(feature = "const_ptr_offset_from", since = "1.65.0")]
     #[inline(always)]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn offset_from(self, origin: *const T) -> isize