fix: intensities error

[jmnavarrete]

This pull request enhances the flexibility and robustness of the pointcloud_to_laserscan nodelet by allowing configurable handling of the intensity field in incoming point clouds. The main improvements are the introduction of a parameter for specifying the intensity field name, safer processing when the field is missing, and clearer code structure for point cloud iteration.

Configurable intensity field support

• Added a new ROS parameter intensity_field_name to allow users to specify which field in the point cloud should be used for intensity values, making the nodelet compatible with different point cloud formats. (src/pointcloud_to_laserscan_nodelet.cpp, include/pointcloud_to_laserscan/pointcloud_to_laserscan_nodelet.h) [1] [2]

• Implemented a helper function hasField to check for the presence of the specified intensity field in the incoming point cloud, improving robustness and error handling. (src/pointcloud_to_laserscan_nodelet.cpp)

Robust handling of missing intensity field

• Added logic to use a default intensity value of 0.0 and issue a warning if the specified intensity field is not found, ensuring the nodelet continues to function even with incomplete data. (src/pointcloud_to_laserscan_nodelet.cpp) [1] [2]

Code clarity and maintainability

• Refactored the point cloud iteration in cloudCb to separate cases for when the intensity field is present and absent, improving code readability and maintainability. (src/pointcloud_to_laserscan_nodelet.cpp) [1] [2]

• Minor formatting improvements for debug messages to enhance log clarity. (src/pointcloud_to_laserscan_nodelet.cpp)