Feature: ros2 port for all filters

[berend-kupers]

Hello,

I have added ROS2 support for the following filters, which did have support in noetic-devel:

• polygon filter
• scan blob filter
• sector filter

Key changes

• Port polygon filter to ROS2
• Port scan blob filter to ROS2
• Port sector filter to ROS2
• Port launch test for polygon filter and speckle filter to ROS2
• Port unit tests for speckle filter and scan shadows filter to ROS2
• Added "remove_shadow_startpoint" parameter to scan shadows filter, which wasn´t included in the port to ROS2

Benefits:

• More filters available in ROS2

Functionality Status:

• No changes have been made to the (default) functionality of other filters

Note: I want to mention two issues that I've noticed in the already ported laser filters, which would be best to fix in the filters package.

1. In box_filter and speckle_filter a (lifecycle-) node is created to create a tf listener (box_filter) and to create a on_set_parameters_callback (speckle_filter). When you start a filter chain and rename the node via launch files, it overrides the name for all node instances. So you get the error:

Publisher already registered for provided node name.

2. Dynamically setting a parameter doesn´t seem to work, even though the speckles_filter does have an on_set_parameters_callback implemented. If I use ros2 param set ..., I get the error:

Setting parameter failed: parameter 'filter2.params.filter_type' cannot be set because it is read-only

I think these parameters are set to read-only in the filters package.

Please let me know if you have any feedback. I would be happy to make any necessary changes.

Kind regards,

Berend Kupers Lowpad