fix(pid_longitudinal_controller): better slope compensation

[takayuki5168]

Description

Depends on #5090

In the case where the slope angle is positive before the goal and negative after the goal as shown in the figure, the current slope compensation works in the opposite direction.

Tests performed

psim

Effects on system behavior

Better slope compensation when arriving at the goal.

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[codecov]

Codecov Report

Patch coverage: 31.57% and project coverage change: -0.02% ⚠️

Comparison is base (ec99b2f) 15.02% compared to head (02c0c52) 15.00%.
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5095      +/-   ##
==========================================
- Coverage   15.02%   15.00%   -0.02%     
==========================================
  Files        1608     1608              
  Lines      111740   111712      -28     
  Branches    34645    34641       -4     
==========================================
- Hits        16788    16762      -26     
- Misses      76244    76248       +4     
+ Partials    18708    18702       -6     

Flag	Coverage Δ		*Carryforward flag
differential	41.28% <31.57%> (?)
total	15.00% <ø> (-0.03%)	⬇️	Carriedforward from ec99b2f

*This pull request uses carry forward flags. Click here to find out more.

Files Changed	Coverage Δ
...dinal_controller/longitudinal_controller_utils.hpp	35.00% <ø> (ø)
...nal_controller/src/pid_longitudinal_controller.cpp	39.24% <0.00%> (-0.48%)	⬇️
...roller/test/test_longitudinal_controller_utils.cpp	51.20% <ø> (-1.75%)	⬇️
...avior_velocity_intersection_module/src/manager.cpp	18.57% <ø> (ø)
...ction_module/src/scene_merge_from_private_road.cpp	0.00% <ø> (ø)
...n_planner/src/lanelet2_plugins/default_planner.cpp	21.80% <ø> (ø)
...elocity_smoother/motion_velocity_smoother_node.hpp	0.00% <ø> (ø)
...ity_smoother/src/motion_velocity_smoother_node.cpp	28.25% <ø> (-0.22%)	⬇️
...l_controller/src/longitudinal_controller_utils.cpp	79.31% <85.71%> (-3.77%)	⬇️

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[TakaHoribe]

LGTM.

Note: we need a trajectory even after the goal point for a few meters to get the slope information. This should be implemented in the goal planner, I guess?