fix(autoware_obstacle_stop_planner): fix cppcheck warnings

[veqcc]

Description

Fixed the following cppcheck warnings

planning/autoware_obstacle_stop_planner/src/adaptive_cruise_control.hpp:206:10: style: inconclusive: Technically the member function 'autoware::motion_planning::AdaptiveCruiseController::calcThreshDistToForwardObstacle' can be const. [functionConst]
  double calcThreshDistToForwardObstacle(const double current_vel, const double obj_vel);
         ^
planning/autoware_obstacle_stop_planner/src/adaptive_cruise_control.cpp:575:34: note: Technically the member function 'autoware::motion_planning::AdaptiveCruiseController::calcThreshDistToForwardObstacle' can be const.
double AdaptiveCruiseController::calcThreshDistToForwardObstacle(
                                 ^
planning/autoware_obstacle_stop_planner/src/adaptive_cruise_control.hpp:206:10: note: Technically the member function 'autoware::motion_planning::AdaptiveCruiseController::calcThreshDistToForwardObstacle' can be const.
  double calcThreshDistToForwardObstacle(const double current_vel, const double obj_vel);
         ^
planning/autoware_obstacle_stop_planner/src/adaptive_cruise_control.hpp:207:10: style: inconclusive: Technically the member function 'autoware::motion_planning::AdaptiveCruiseController::calcBaseDistToForwardObstacle' can be const. [functionConst]
  double calcBaseDistToForwardObstacle(const double current_vel, const double obj_vel);
         ^
planning/autoware_obstacle_stop_planner/src/adaptive_cruise_control.cpp:592:34: note: Technically the member function 'autoware::motion_planning::AdaptiveCruiseController::calcBaseDistToForwardObstacle' can be const.
double AdaptiveCruiseController::calcBaseDistToForwardObstacle(
                                 ^
planning/autoware_obstacle_stop_planner/src/adaptive_cruise_control.hpp:207:10: note: Technically the member function 'autoware::motion_planning::AdaptiveCruiseController::calcBaseDistToForwardObstacle' can be const.
  double calcBaseDistToForwardObstacle(const double current_vel, const double obj_vel);
         ^
planning/autoware_obstacle_stop_planner/src/debug_marker.hpp:80:52: performance: Function 'getValues()' should return member 'values_' by const reference. [returnByReference]
  std::array<double, static_cast<int>(TYPE::SIZE)> getValues() const { return values_; }
                                                   ^
planning/autoware_obstacle_stop_planner/src/adaptive_cruise_control.cpp:114:0: style: The function 'sign' is never used. [unusedFunction]
constexpr double sign(const double value)
^

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How was this PR tested?

Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 29.76%. Comparing base (5778e01) to head (2b1bc25).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9388      +/-   ##
==========================================
- Coverage   29.77%   29.76%   -0.01%     
==========================================
  Files        1338     1339       +1     
  Lines      103364   103381      +17     
  Branches    40234    40234              
==========================================
+ Hits        30773    30774       +1     
- Misses      69606    69624      +18     
+ Partials     2985     2983       -2     

Flag	Coverage Δ		*Carryforward flag
differential	8.53% <ø> (?)
total	29.77% <ø> (-0.01%)	⬇️	Carriedforward from 5778e01

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