fix(cmake): vendor ankerl::unordered_dense to fix ROS buildfarm

ROS buildfarm sets FETCHCONTENT_FULLY_DISCONNECTED=ON, so the prior
CPMAddPackage(unordered_dense) silently no-op'd and left
unordered_dense::unordered_dense undefined, breaking all four ROS2
distro builds on PR #100. unordered_dense is a single-header library
with exactly one consumer (applyVizLossyPreprocessing in
ros_msg_utils.cpp), and Ubuntu 22.04 (humble) has no apt package, so
vendoring is the most reliable fix and matches the existing pattern
under cloudini_lib/include/cloudini_lib/contrib/ (span.hpp, nanocdr.hpp).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Davide Faconti

cloudini_lib/CMakeLists.txt

@@ -37,18 +37,6 @@ find_or_download_zstd(${CLOUDINI_FORCE_VENDORED_DEPS})
 include(cmake/find_or_download_lz4.cmake)
 find_or_download_lz4(${CLOUDINI_FORCE_VENDORED_DEPS})
 
-# ankerl::unordered_dense — single-header MIT, used by ros_msg_utils.cpp's
-# applyVizLossyPreprocessing for fast voxel-dedup hash set.
-find_package(unordered_dense QUIET)
-if(NOT TARGET unordered_dense::unordered_dense)
-  CPMAddPackage(
-    NAME unordered_dense
-    GITHUB_REPOSITORY martinus/unordered_dense
-    VERSION 4.8.1
-  )
-endif()
-
-
 ##################################################################################
 
 # ----  Trick to pass an absolute path to C++ code  ----
@@ -130,7 +118,6 @@ target_link_libraries(cloudini_lib
   PRIVATE
     $<BUILD_INTERFACE:LZ4::lz4_static>
     $<BUILD_INTERFACE:${CLOUDINI_ZSTD_TARGET}>
-    $<BUILD_INTERFACE:unordered_dense::unordered_dense>
   PUBLIC
     ${PCL_COMMON_LIBRARIES}
     ${PCL_IO_LIBRARIES}

cloudini_lib/include/cloudini_lib/contrib/ankerl/stl.h

@@ -0,0 +1,83 @@
+///////////////////////// ankerl::unordered_dense::{map, set} /////////////////////////
+
+// A fast & densely stored hashmap and hashset based on robin-hood backward shift deletion.
+// Version 4.8.1
+// https://github.com/martinus/unordered_dense
+//
+// Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2022 Martin Leitner-Ankerl <martin.ankerl@gmail.com>
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#ifndef ANKERL_STL_H
+#define ANKERL_STL_H
+
+#include <array>            // for array
+#include <cstdint>          // for uint64_t, uint32_t, std::uint8_t, UINT64_C
+#include <cstring>          // for size_t, memcpy, memset
+#include <functional>       // for equal_to, hash
+#include <initializer_list> // for initializer_list
+#include <iterator>         // for pair, distance
+#include <limits>           // for numeric_limits
+#include <memory>           // for allocator, allocator_traits, shared_ptr
+#include <optional>         // for optional
+#include <stdexcept>        // for out_of_range
+#include <string>           // for basic_string
+#include <string_view>      // for basic_string_view, hash
+#include <tuple>            // for forward_as_tuple
+#include <type_traits>      // for enable_if_t, declval, conditional_t, ena...
+#include <utility>          // for forward, exchange, pair, as_const, piece...
+#include <vector>           // for vector
+
+// <memory_resource> includes <mutex>, which fails to compile if
+// targeting GCC >= 13 with the (rewritten) win32 thread model, and
+// targeting Windows earlier than Vista (0x600).  GCC predefines
+// _REENTRANT when using the 'posix' model, and doesn't when using the
+// 'win32' model.
+#if defined __MINGW64__ && defined __GNUC__ && __GNUC__ >= 13 && !defined _REENTRANT
+// _WIN32_WINNT is guaranteed to be defined here because of the
+// <cstdint> inclusion above.
+#    ifndef _WIN32_WINNT
+#        error "_WIN32_WINNT not defined"
+#    endif
+#    if _WIN32_WINNT < 0x600
+#        define ANKERL_MEMORY_RESOURCE_IS_BAD() 1 // NOLINT(cppcoreguidelines-macro-usage)
+#    endif
+#endif
+#ifndef ANKERL_MEMORY_RESOURCE_IS_BAD
+#    define ANKERL_MEMORY_RESOURCE_IS_BAD() 0 // NOLINT(cppcoreguidelines-macro-usage)
+#endif
+
+#if defined(__has_include) && !defined(ANKERL_UNORDERED_DENSE_DISABLE_PMR)
+#    if __has_include(<memory_resource>) && !ANKERL_MEMORY_RESOURCE_IS_BAD()
+#        define ANKERL_UNORDERED_DENSE_PMR std::pmr // NOLINT(cppcoreguidelines-macro-usage)
+#        include <memory_resource>                  // for polymorphic_allocator
+#    elif __has_include(<experimental/memory_resource>)
+#        define ANKERL_UNORDERED_DENSE_PMR std::experimental::pmr // NOLINT(cppcoreguidelines-macro-usage)
+#        include <experimental/memory_resource>                   // for polymorphic_allocator
+#    endif
+#endif
+
+#if defined(_MSC_VER) && defined(_M_X64)
+#    include <intrin.h>
+#    pragma intrinsic(_umul128)
+#endif
+
+#endif