fix: use size_t instead of uint64_t in play_options YAML converter

[wep21]

• avoid build error on apple silicon below.

/Users/daisuke/workspace/rolling/src/ros2/rosbag2/rosbag2_transport/src/rosbag2_transport/play_options.cpp:65:3: error: no matching function for call to 'optional_assign'
  optional_assign<uint64_t>(node, "read_ahead_queue_size", play_options.read_ahead_queue_size);
  ^~~~~~~~~~~~~~~~~~~~~~~~~
/Users/daisuke/workspace/rolling/install/rosbag2_storage/include/rosbag2_storage/rosbag2_storage/yaml.hpp:42:6: note: candidate function template not viable: no known conversion from 'size_t' (aka 'unsigned long') to 'unsigned long long &' for 3rd argument
void optional_assign(const Node & node, std::string field, T & assign_to)
     ^
1 error generated.                                        
make[2]: *** [CMakeFiles/rosbag2_transport.dir/src/rosbag2_transport/play_options.cpp.o] Error 1
make[1]: *** [CMakeFiles/rosbag2_transport.dir/all] Error 2
make: *** [all] Error 2
--- stderr: rosbag2_transport                             
/Users/daisuke/workspace/rolling/src/ros2/rosbag2/rosbag2_transport/src/rosbag2_transport/play_options.cpp:65:3: error: no matching function for call to 'optional_assign'
  optional_assign<uint64_t>(node, "read_ahead_queue_size", play_options.read_ahead_queue_size);
  ^~~~~~~~~~~~~~~~~~~~~~~~~
/Users/daisuke/workspace/rolling/install/rosbag2_storage/include/rosbag2_storage/rosbag2_storage/yaml.hpp:42:6: note: candidate function template not viable: no known conversion from 'size_t' (aka 'unsigned long') to 'unsigned long long &' for 3rd argument
void optional_assign(const Node & node, std::string field, T & assign_to)
     ^
1 error generated.
make[2]: *** [CMakeFiles/rosbag2_transport.dir/src/rosbag2_transport/play_options.cpp.o] Error 1
make[1]: *** [CMakeFiles/rosbag2_transport.dir/all] Error 2
make: *** [all] Error 2
---
Failed   <<< rosbag2_transport [4.53s, exited with code 2]

[fujitatomoya]

@MichaelOrlov could you take a look when you have time?

[MichaelOrlov]

LGTM.

[MichaelOrlov]

Gist: https://gist.githubusercontent.com/MichaelOrlov/12bc9bc69a93cd9f459263c138bfe08f/raw/edbf5838ca762d27c037228a03f45119f8d67ffd/ros2.repos
BUILD args: --packages-above-and-dependencies rosbag2_transport rosbag2_tests
TEST args: --packages-above rosbag2_transport rosbag2_tests
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/13398

• Linux
• Linux-aarch64
• Windows