MPPI: Do not set params success in dynamic params callback to allow changing params in other plugins

[pepisg]

---

Basic Info

Info	Theres a bug when setting params from other plugins when using mppi
Ticket(s) this addresses
Primary OS tested on	(Ubuntu, MacOS, Windows)
Robotic platform tested on	(Steve's Robot, gazebo simulation of Tally, hardware turtlebot)
Does this PR contain AI generated software?	(No; Yes and it is marked inline in the code)

---

Description of contribution in a few bullet points

Currently, the parameters handler library in the MPPI will return failure when trying to set a parameter in the controller server node that does not belong to the MPPI plugin. This is because rclcpp will stop processing dynamic params callbacks when one of them returns falure, see ros2/rclcpp#2735 for details

Description of documentation updates required from your changes

Description of how this change was tested

---

Future work that may be required in bullet points

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

[SteveMacenski]

There are some test failures: https://app.circleci.com/pipelines/github/ros-navigation/navigation2/13610/workflows/4eea23eb-3231-4ea7-a2fe-ebf0d92506cb/jobs/40607/tests

• These can be deleted now: https://github.com/ros-navigation/navigation2/blob/main/nav2_mppi_controller/test/parameter_handler_test.cpp#L270-L276
• Removing the undeclared variables that are deleted from the first bullet here and the expects: https://github.com/ros-navigation/navigation2/blob/main/nav2_mppi_controller/test/parameter_handler_test.cpp#L278-L297

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ
nav2_mppi_controller/src/parameters_handler.cpp	100.00% <ø> (ø)

... and 2 files with indirect coverage changes