revert get_immutable() -> read()

Signed-off-by: martinvuyk <[email protected]>

stdlib/src/builtin/sort.mojo

@@ -213,7 +213,7 @@ fn _quicksort[
 
     # Work with an immutable span so we don't run into exclusivity problems with
     # the List[Span].
-    var imm_span = span.read()
+    var imm_span = span.get_immutable()
     alias ImmSpan = __type_of(imm_span)
 
     var stack = List[ImmSpan](capacity=_estimate_initial_height(size))
@@ -341,7 +341,9 @@ fn _stable_sort_impl[
         while j + merge_size < size:
             var span1 = span[j : j + merge_size]
             var span2 = span[j + merge_size : min(size, j + 2 * merge_size)]
-            _merge[cmp_fn](span1.read(), span2.read(), temp_buff)
+            _merge[cmp_fn](
+                span1.get_immutable(), span2.get_immutable(), temp_buff
+            )
             for i in range(merge_size + len(span2)):
                 span[j + i] = temp_buff[i]
             j += 2 * merge_size

stdlib/src/utils/span.mojo

@@ -347,7 +347,7 @@ struct Span[
         for element in self:
             element[] = value
 
-    fn read(self) -> Span[T, _lit_mut_cast[origin, False].result]:
+    fn get_immutable(self) -> Span[T, _lit_mut_cast[origin, False].result]:
         """
         Return an immutable version of this span.