Rename slice_from_ptr_range_const -> const_slice_from_ptr_range

This is in line with other `const fn` features.

Author: WaffleLapkin

library/core/src/slice/raw.rs

@@ -213,7 +213,7 @@ pub const fn from_mut<T>(s: &mut T) -> &mut [T] {
 ///
 /// [valid]: ptr#safety
 #[unstable(feature = "slice_from_ptr_range", issue = "89792")]
-#[rustc_const_unstable(feature = "slice_from_ptr_range_const", issue = "89792")]
+#[rustc_const_unstable(feature = "const_slice_from_ptr_range", issue = "89792")]
 pub const unsafe fn from_ptr_range<'a, T>(range: Range<*const T>) -> &'a [T] {
     // SAFETY: the caller must uphold the safety contract for `from_ptr_range`.
     unsafe { from_raw_parts(range.start, range.end.sub_ptr(range.start)) }

src/test/ui/const-ptr/allowed_slices.rs

@@ -2,7 +2,7 @@
 #![feature(
     const_slice_from_raw_parts,
     slice_from_ptr_range,
-    slice_from_ptr_range_const,
+    const_slice_from_ptr_range,
     pointer_byte_offsets,
     const_pointer_byte_offsets
 )]

src/test/ui/const-ptr/forbidden_slices.rs

@@ -1,7 +1,7 @@
 #![feature(
     const_slice_from_raw_parts,
     slice_from_ptr_range,
-    slice_from_ptr_range_const,
+    const_slice_from_ptr_range,
     pointer_byte_offsets,
     const_pointer_byte_offsets
 )]