Simplify namespaced bringups and multirobot sim

[luca-della-vedova]

Basic Info

Info	Please fill out this column
Ticket(s) this addresses	N/A, see ros-navigation/nav2_minimal_turtlebot_simulation#15 for background
Primary OS tested on	Ubuntu 24.04 Jazzy
Robotic platform tested on	TB3 (single / multiple) and TB4 sim on Gazebo Harmonic
Does this PR contain AI generated software?	No

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Description of contribution in a few bullet points

Reworked namespacing, no more having an rviz config with absolute topics and one for namespaced topics that relies on string substitution, but just a single one that will use the namespace passed to rviz to be resolved, for example:

## BEFORE:
# rviz_default_view.rviz, subscribing to laser scan
topic: /scan
# rviz_namespaced_view.rviz, subscribing to laser scan
topic: <robot_namespace>/scan

## AFTER:
# rviz_default_view.rviz
topic: scan
# When running, just set the rviz namespace, when none is specified it will automatically default to /scan

Note that topic names were also hardcoded in the nav2 params, to my understanding most of the duplication in the config files for the multirobot sim was really just to make sure different robots are subscribed to different topics, however now with proper namespace support all the robots can just reuse the same config file without needing to change topics, do string substitution or anything like that.

Description of documentation updates required from your changes

Not sure, the previous behavior should still work, but now bringing up multiple robots should require significantly less work / config file duplication.

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Future work that may be required in bullet points

There is just one rough edge (and the only code change in this PR) that I had to hack to make this work, which I'm not terribly happy with (but not too sure there is any better way), here.

The costmap topics are in the namespace <chosen_namespace>/[local, global]_costmap, which makes it tricky for users to pass a local topic to subscribe to such as scan, since that would be parsed as <chosen_namespace>/local_costmap/scan which is clearly not what most cases would do.
I added that "hack" to manually go up one namespace and make sure that the topic name is relative to the chosen namespace, not the costmap local one. It works well but I can't say I'm too happy with it (I was really hoping there would be a .. operator for topics so I could specify it as ../scan but alas that seems to not be the case).

For Maintainers:

• Check that any new parameters added are updated in docs.nav2.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

[codecov]

Codecov Report

Attention: Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
nav2_costmap_2d/src/costmap_layer.cpp	85.71%	1 Missing ⚠️

Files with missing lines	Coverage Δ
nav2_controller/src/controller_server.cpp	84.49% <100.00%> (ø)
...tmap_2d/include/nav2_costmap_2d/costmap_2d_ros.hpp	100.00% <ø> (ø)
...stmap_2d/include/nav2_costmap_2d/costmap_layer.hpp	100.00% <ø> (ø)
nav2_costmap_2d/plugins/obstacle_layer.cpp	80.59% <100.00%> (+0.06%)	⬆️
nav2_costmap_2d/plugins/range_sensor_layer.cpp	78.77% <100.00%> (+0.10%)	⬆️
nav2_costmap_2d/plugins/static_layer.cpp	69.41% <100.00%> (+0.03%)	⬆️
nav2_costmap_2d/src/costmap_2d_ros.cpp	89.13% <100.00%> (+0.06%)	⬆️
nav2_planner/src/planner_server.cpp	91.56% <100.00%> (ø)
nav2_costmap_2d/src/costmap_layer.cpp	49.13% <85.71%> (+2.34%)	⬆️

... and 4 files with indirect coverage changes

[SteveMacenski]

STEVE: Update STVL/NPVL

[luca-della-vedova]

I realized I forgot to properly cleanup the use_namespace parameter throughout the codebase since it's not used anymore so I did it in 7ad9241.

[SteveMacenski]

Beyond this topic on map_topic, I approve all other changes and happy to merge once resolved :-)

[SteveMacenski]

Small docs update, then good to merge. I really appreciate your time and patience, I agree this is a really nice simplification and I'm sure every time I don't need to update N files with new parameter changes, I'll think of this!