[CCCL] 瘦身 + 补全: 移除 cudax/python/libcudacxx-tests 冗余文件, 新增 c2h 测试助手 + cmake 构建系统 + 8 个 CUDA thrust examples

变更摘要:
- 删除: cudax/ (783 files, 7.2M) — 实验性组件，竞赛不需要
- 删除: python/ (226 files, 2.0M) — Python 绑定，竞赛不需要
- 删除: libcudacxx/{test,benchmarks,codegen,cmake,share} (4432 files, 31M)
  保留: libcudacxx/include/ (1463 headers, cuda::std 编译依赖)
- 新增: c2h/ (27 files) — CUB Catch2 测试辅助头文件，编译 243 个测试必需
- 新增: cmake/ (29 files) — CCCL 原生 CMake 构建系统
- 新增: thrust/examples/cuda/ (7 files) + cpp_integration/ (1 file)
  async_reduce, custom_temporary_allocation, explicit_cuda_stream,
  global_device_vector, range_view, unwrap_pointer, wrap_pointer, device

结果: cccl_upstream 从 74M→35M (瘦身 53%), 核心内容 100% 保留:
  27/27 tuning headers, 78 benchmarks, 243 tests,
  60 thrust examples, 18 CUB examples, 全部编译头文件

cccl_upstream/cudax/examples/stf/binary_fhe.cu

@@ -1,201 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// Part of CUDASTF in CUDA C++ Core Libraries,
-// 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
-// SPDX-FileCopyrightText: Copyright (c) 2022-2024 NVIDIA CORPORATION & AFFILIATES.
-//
-//===----------------------------------------------------------------------===//
-
-/**
- * @file
- * @brief A toy example to illustrate how we can compose logical operations
- *        over encrypted data
- */
-
-#include <cuda/experimental/stf.cuh>
-
-using namespace cuda::experimental::stf;
-
-class ciphertext;
-
-class plaintext
-{
-public:
-  plaintext(const context& ctx)
-      : ctx(ctx)
-  {}
-
-  plaintext(context& ctx, std::vector<char> v)
-      : values(v)
-      , ctx(ctx)
-  {
-    l = ctx.logical_data(&values[0], values.size());
-  }
-
-  void set_symbol(std::string s)
-  {
-    l.set_symbol(s);
-    symbol = s;
-  }
-
-  std::string get_symbol() const
-  {
-    return symbol;
-  }
-
-  std::string symbol;
-
-  const logical_data<slice<char>>& data() const
-  {
-    return l;
-  }
-
-  logical_data<slice<char>>& data()
-  {
-    return l;
-  }
-
-  // This will asynchronously fill string s
-  void convert_to_vector(std::vector<char>& v)
-  {
-    ctx.host_launch(l.read()).set_symbol("to_vector")->*[&](auto dl) {
-      v.resize(dl.size());
-      for (size_t i = 0; i < dl.size(); i++)
-      {
-        v[i] = dl(i);
-      }
-    };
-  }
-
-  ciphertext encrypt() const;
-
-  logical_data<slice<char>> l;
-
-private:
-  std::vector<char> values;
-  mutable context ctx;
-};
-
-class ciphertext
-{
-public:
-  ciphertext(const context& ctx)
-      : ctx(ctx)
-  {}
-
-  plaintext decrypt() const
-  {
-    plaintext p(ctx);
-    p.l = ctx.logical_data(shape_of<slice<char>>(l.shape().size()));
-    // fprintf(stderr, "Decrypting...\n");
-    ctx.parallel_for(l.shape(), l.read(), p.l.write()).set_symbol("decrypt")->*
-      [] _CCCL_DEVICE(size_t i, auto dctxt, auto dptxt) {
-        dptxt(i) = char((dctxt(i) >> 32));
-        // printf("DECRYPT %ld : %lx -> %x\n", i, dctxt(i), (int) dptxt(i));
-      };
-    return p;
-  }
-
-  ciphertext operator|(const ciphertext& other) const
-  {
-    ciphertext result(ctx);
-    result.l = ctx.logical_data(data().shape());
-
-    ctx.parallel_for(data().shape(), data().read(), other.data().read(), result.data().write()).set_symbol("OR")->*
-      [] _CCCL_DEVICE(size_t i, auto d_c1, auto d_c2, auto d_res) {
-        d_res(i) = d_c1(i) | d_c2(i);
-      };
-
-    return result;
-  }
-
-  ciphertext operator&(const ciphertext& other) const
-  {
-    ciphertext result(ctx);
-    result.l = ctx.logical_data(data().shape());
-
-    ctx.parallel_for(data().shape(), data().read(), other.data().read(), result.data().write()).set_symbol("AND")->*
-      [] _CCCL_DEVICE(size_t i, auto d_c1, auto d_c2, auto d_res) {
-        d_res(i) = d_c1(i) & d_c2(i);
-      };
-
-    return result;
-  }
-
-  ciphertext operator~() const
-  {
-    ciphertext result(ctx);
-    result.l = ctx.logical_data(data().shape());
-    ctx.parallel_for(data().shape(), data().read(), result.data().write()).set_symbol("NOT")->*
-      [] _CCCL_DEVICE(size_t i, auto d_c, auto d_res) {
-        d_res(i) = ~d_c(i);
-      };
-
-    return result;
-  }
-
-  const logical_data<slice<uint64_t>>& data() const
-  {
-    return l;
-  }
-
-  logical_data<slice<uint64_t>>& data()
-  {
-    return l;
-  }
-
-  logical_data<slice<uint64_t>> l;
-
-private:
-  mutable context ctx;
-};
-
-ciphertext plaintext::encrypt() const
-{
-  ciphertext c(ctx);
-  c.l = ctx.logical_data(shape_of<slice<uint64_t>>(l.shape().size()));
-
-  ctx.parallel_for(l.shape(), l.read(), c.l.write()).set_symbol("encrypt")->*
-    [] _CCCL_DEVICE(size_t i, auto dptxt, auto dctxt) {
-      // A super safe encryption !
-      dctxt(i) = ((uint64_t) (dptxt(i)) << 32 | 0x4);
-    };
-
-  return c;
-}
-
-template <typename T>
-T circuit(const T& a, const T& b)
-{
-  return (~((a | ~b) & (~a | b)));
-}
-
-int main()
-{
-  context ctx;
-
-  std::vector<char> vA{3, 3, 2, 2, 17};
-  plaintext pA(ctx, vA);
-  pA.set_symbol("A");
-
-  std::vector<char> vB{1, 7, 7, 7, 49};
-  plaintext pB(ctx, vB);
-  pB.set_symbol("B");
-
-  auto eA  = pA.encrypt();
-  auto eB  = pB.encrypt();
-  auto out = circuit(eA, eB);
-
-  std::vector<char> v_out;
-  out.decrypt().convert_to_vector(v_out);
-
-  ctx.finalize();
-
-  for (size_t i = 0; i < v_out.size(); i++)
-  {
-    char expected = circuit(vA[i], vB[i]);
-    EXPECT(expected == v_out[i]);
-  }
-}