[lidar] speedup create_cloud

[PierrickKoch]

Up to 4000 times faster, depending on points cloud size. Don't use struct pack_into over each point, copy numpy raw buffer instead.

• See profiling and test scripts at [1].
• Inspired from eric-wieser/ros_numpy [2].
• Besides, fromstring is deprecated [3].

[1] https://gist.github.com/PierrickKoch/01181660d3427990db64056df43257a5#file-lidar_timeit-py [2] https://github.com/eric-wieser/ros_numpy/blob/master/src/ros_numpy/point_cloud2.py [3] https://github.com/numpy/numpy/blob/main/numpy/core/src/multiarray/multiarraymodule.c#L2248

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This change is 

[ksuszka]

Isn't this duplicate of https://github.com/carla-simulator/ros-bridge/pull/557 ? In any case it would be nice to have one of those merged.