[INFRA] Import NVIDIA/CCCL upstream as optimization reference library

CCCL (CUDA C++ Core Libraries) provides:
- CUB: device/block/warp-level GPU primitives (reduce, scan, sort, topk)
- Thrust: high-level parallel algorithms (transform_reduce, sort, scan)
- libcudacxx: CUDA C++ standard library (atomics, barriers, memory)
- cudax: experimental features (memory resources, allocators)
- Tuning policies: per-SM hardware-specific algorithm parameters

Competition optimization vectors mapped to CCCL:
- Output TPS (83% weight): warp_reduce, block_reduce, device_topk
- Input TPS (14% weight): device_scan, block_load, prefetch
- Cache TPS (3% weight): prefix caching strategy patterns
- Memory (0.9 util): pooled/cached/buddy allocators

Source: https://github.com/NVIDIA/cccl (shallow clone, HEAD only)
License: Apache-2.0

cccl_upstream/libcudacxx/test/support/placement_new.h

@@ -0,0 +1,32 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef PLACEMENT_NEW_HPP
+#define PLACEMENT_NEW_HPP
+
+#include "test_macros.h"
+
+// CUDA always defines placement new/delete for device code.
+#if !_CCCL_CUDA_COMPILATION()
+
+#  include <stddef.h> // Avoid depending on the C++ standard library.
+
+void* operator new(size_t, void* p)
+{
+  return p;
+}
+void* operator new[](size_t, void* p)
+{
+  return p;
+}
+void operator delete(void*, void*) {}
+void operator delete[](void*, void*) {}
+
+#endif // !_CCCL_CUDA_COMPILATION()
+
+#endif // PLACEMENT_NEW_HPP