refactor(goal_planner): move unnecessary member functions

[soblin]

Description

for achieving #9514

some member functions do not need to be member function, so move them to free functions,

Related links

Parent Issue:

• Link

How was this PR tested?

• evaluator

Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 41 lines in your changes missing coverage. Please review.

Project coverage is 29.46%. Comparing base (c1bbd68) to head (af0316b).
Report is 24 commits behind head on main.

Files with missing lines	Patch %	Lines
...th_goal_planner_module/src/goal_planner_module.cpp	0.00%	41 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9522      +/-   ##
==========================================
- Coverage   29.47%   29.46%   -0.02%     
==========================================
  Files        1440     1445       +5     
  Lines      108556   108610      +54     
  Branches    41499    41501       +2     
==========================================
  Hits        32001    32001              
- Misses      73443    73496      +53     
- Partials     3112     3113       +1     

Flag	Coverage Δ		*Carryforward flag
differential	0.52% <0.00%> (?)
total	29.49% <ø> (+0.01%)	⬆️	Carriedforward from c1bbd68

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