feat(obstacle_cruise_planner): single slow down virtual wall

[takayuki5168]

Description

Without this PR, the start/end virtual walls are visualized for slow down, which becomes messy with a lot of obstacles.
This PR makes the slow down virtual wall single as follows.

Before this PR

After this PR
Before reaching the slow down start position, the virtual wall is visualized at the slow down start position.

While planning slow down, the virtual wall is visualized at the front of the ego position.

Tests performed

planning simulator

Effects on system behavior

Nothing

Pre-review checklist for the PR author

The PR author must check the checkboxes below when creating the PR.

• I've confirmed the contribution guidelines.
• The PR follows the pull request guidelines.

In-review checklist for the PR reviewers

The PR reviewers must check the checkboxes below before approval.

• The PR follows the pull request guidelines.

Post-review checklist for the PR author

The PR author must check the checkboxes below before merging.

• There are no open discussions or they are tracked via tickets.

After all checkboxes are checked, anyone who has write access can merge the PR.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.01 ⚠️

Comparison is base (ff8c637) 15.05% compared to head (a036c3e) 15.05%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4374      +/-   ##
==========================================
- Coverage   15.05%   15.05%   -0.01%     
==========================================
  Files        1508     1508              
  Lines      103776   103779       +3     
  Branches    31715    31718       +3     
==========================================
- Hits        15623    15622       -1     
- Misses      71125    71127       +2     
- Partials    17028    17030       +2     

Flag	Coverage Δ		*Carryforward flag
differential	8.51% <0.00%> (?)
total	15.05% <ø> (+<0.01%)	⬆️	Carriedforward from ff8c637

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

Impacted Files	Coverage Δ
...include/obstacle_cruise_planner/common_structs.hpp	9.52% <ø> (ø)
planning/obstacle_cruise_planner/src/node.cpp	12.48% <0.00%> (-0.04%)	⬇️
.../obstacle_cruise_planner/src/planner_interface.cpp	7.82% <0.00%> (-0.37%)	⬇️

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[takayuki5168]

@purewater0901 Could you approve the PR.