fix(behavior_path_planner): drivable area front nearest segment index

[takayuki5168]

Description

Without this PR, closest_idx from findNearestSegmentIndex is considered for calculating minimum index of lateral distance.
However, ideally, this closest index should be considered when minimum index of lateral distance itself is not found.
Due to the current implementation, unexpected closest index is used in some cases.

This PR calculates the minimum index of lateral distance first, and only if not found, closest index from findNearestSegmentIndex is used instead.

Tests performed

planning simulator
scenario simulator (https://evaluation.tier4.jp/evaluation/reports/e00f9794-72e8-59f4-95f8-c737db40ad67?project_id=prd_jt)

Effects on system behavior

Nothing

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[codecov]

Codecov Report

Patch coverage: 55.55% and project coverage change: -0.04% ⚠️

Comparison is base (5f15fd3) 14.86% compared to head (edecb33) 14.83%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4489      +/-   ##
==========================================
- Coverage   14.86%   14.83%   -0.04%     
==========================================
  Files        1519     1519              
  Lines      104940   105725     +785     
  Branches    31971    32519     +548     
==========================================
+ Hits        15599    15681      +82     
- Misses      72288    72908     +620     
- Partials    17053    17136      +83     

Flag	Coverage Δ		*Carryforward flag
differential	13.22% <55.55%> (?)
total	14.85% <ø> (-0.01%)	⬇️	Carriedforward from 5f15fd3

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

Files Changed	Coverage Δ
planning/behavior_path_planner/src/utils/utils.cpp	15.66% <55.55%> (-0.04%)	⬇️

... and 9 files with indirect coverage changes

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