[oneDPL][ranges] Add inplace_merge (#643)

Author: dmitriy-sobolev

source/elements/oneDPL/source/parallel_api/parallel_range_api.rst

@@ -408,6 +408,15 @@ Sorting and Merge
         merge (ExecutionPolicy&& pol, R1&& r1, R2&& r2, OutR&& result, Comp comp = {},
                Proj1 proj1 = {}, Proj2 proj2 = {});
 
+    // inplace_merge
+    template <typename ExecutionPolicy, std::ranges::random_access_range R,
+              typename Comp = std::ranges::less, typename Proj = std::identity>
+      requires oneapi::dpl::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> &&
+               std::ranges::sized_range<R> && std::sortable<std::ranges::iterator_t<R>, Comp, Proj>
+      std::ranges::borrowed_iterator_t<R>
+        inplace_merge (ExecutionPolicy&& pol, R&& r, std::ranges::iterator_t<R> middle,
+                       Comp comp = {}, Proj proj = {});
+
   }
 
 Set operations
@@ -493,6 +502,7 @@ Set operations
                                                    std::ranges::borrowed_iterator_t<OutR>>
         set_symmetric_difference (ExecutionPolicy&& pol, R1&& r1, R2&& r2, OutR&& result,
                                  Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
+
   }
 
 Copying Mutating Operations