Use the new declare_or_get_parameter API for nav2_costmap_2d

[leander-dsouza]

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Basic Info

Info	Please fill out this column
Ticket(s) this addresses	#5299
Primary OS tested on	Ubuntu
Robotic platform tested on	N/A
Does this PR contain AI-generated software?	No
Was this PR description generated by AI software?	N/A

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Description of contribution in a few bullet points

• Migrated the get_parameter and declare_parameter fields to use the new declare_or_get_parameter API for nav2_costmap_2d.
• Partially migrated the parameters in costmap_2d_ros.cpp, as the test setup requires these parameters to be declared in the init() function.
• Removed redundant set_parameter() calls in the tests that are followed by declare_parameter calls.

Description of documentation updates required from your changes

• N/A

Description of how this change was tested

• Performed linting validation using pre-commit run --all and testing locally using colcon test

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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
• Should this be backported to current distributions? If so, tag with backport-*.

[leander-dsouza]

Should I replace the Layer's declareParameter() calls as well?

I have tried replacing all node->get_parameter() calls that precede declareParameter() with node->declare_or_get_parameter(), and all the tests pass locally.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
nav2_costmap_2d/plugins/plugin_container_layer.cpp	98.76% <100.00%> (-0.08%)	⬇️
nav2_costmap_2d/src/costmap_2d_ros.cpp	86.41% <100.00%> (-0.14%)	⬇️

... and 7 files with indirect coverage changes

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