Publish collision monitor state

[kaichie]

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Basic Info

Info	Please fill out this column
Ticket(s) this addresses	#3496
Primary OS tested on	Ubuntu
Robotic platform tested on	Dexory Simulation

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Description of contribution in a few bullet points

• Added a new msg in nav2_msgs - CollisionMonitorState.msg
• Publish CollisionMonitor action state
• Also fixed that the first action will not be printed if it is DO_NOTHING
• Also updated the state change logic to check with polygon_name instead of action_type (To handle multiple slowdown polygons correctly)

Description of documentation updates required from your changes

• Added new topic + param, so need to add that to default configs and documentation page

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Future work that may be required in bullet points

• This PR report the CM's action state change based on the input cmd_vel, but I think it will be very useful to publish the polygon state even when the robot is not moving too. Especially for cases like when the stop polygon is triggered(regardless of cmd_vel speed), or when there are points in approach polygon where the robot will not be able to move. (Probably similar requirement as mentioned here)

For Maintainers:

• Check that any new parameters added are updated in navigation.ros.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists

[SteveMacenski]

Looks good in general, most are nit picks and a couple of questions

[AlexeyMerzlyakov]

There are some items, I've mentioned, but in overall, this seems a good approach for me

[SteveMacenski]

Otherwise LGTM, just need the complimentary documentation updates for the new parameter in the config guide + migration guide for the new feature

[kaichie]

Thanks for the review @SteveMacenski and @AlexeyMerzlyakov! Created a PR for updating the config guide + migration guide too.

[SteveMacenski]

LGTM. On Alexey's final call to merge.

[AlexeyMerzlyakov]

Change reviewed: OK.
Local colcon test --packages-select nav2_collision_monitor: OK
Codecov test: OK
Local TB3 simulation verification: OK (CM is working well and publishing a new topic)