GH-48315: [C++] Use FetchContent for bundled Crc32c

Author: raulcd

cpp/cmake_modules/ThirdpartyToolchain.cmake

@@ -3594,11 +3594,7 @@ macro(build_google_cloud_cpp_storage)
     add_dependencies(google_cloud_cpp_dependencies zlib_ep)
   endif()
   add_dependencies(google_cloud_cpp_dependencies crc32c_fc)
-  if(NLOHMANN_JSON_VENDORED)
-    add_dependencies(google_cloud_cpp_dependencies nlohmann_json_fc)
-  else()
-    add_dependencies(google_cloud_cpp_dependencies nlohmann_json::nlohmann_json)
-  endif()
+  add_dependencies(google_cloud_cpp_dependencies nlohmann_json::nlohmann_json)
 
   set(GOOGLE_CLOUD_CPP_STATIC_LIBRARY_STORAGE
       "${GOOGLE_CLOUD_CPP_INSTALL_PREFIX}/lib/${CMAKE_STATIC_LIBRARY_PREFIX}google_cloud_cpp_storage${CMAKE_STATIC_LIBRARY_SUFFIX}"