refactor(pose_instability_detector, ar_tag_based_localizer): specify file path using get_package_share_directory

[KYabuuchi]

Description

By using ament_index_cpp::get_package_share_directory, the path to the config file can be specified from the package path.

Tests performed

colcon test --event-handlers console_cohesion+ \
   --packages-select ar_tag_based_localizer pose_instability_detector

Effects on system behavior

It does not effect the system behavior.

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[KYabuuchi]

@SakodaShintaro please review as a representative 🙏

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (765a596) 15.32% compared to head (6e178b2) 15.32%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
...sed_localizer/ar_tag_based_localizer/test/test.cpp	0.00%	0 Missing and 2 partials ⚠️
...calization/pose_instability_detector/test/test.cpp	0.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5588      +/-   ##
==========================================
- Coverage   15.32%   15.32%   -0.01%     
==========================================
  Files        1721     1721              
  Lines      118559   118560       +1     
  Branches    37995    37998       +3     
==========================================
- Hits        18169    18167       -2     
  Misses      79657    79657              
- Partials    20733    20736       +3     

Flag	Coverage Δ		*Carryforward flag
differential	32.81% <0.00%> (?)
total	15.32% <ø> (-0.01%)	⬇️	Carriedforward from 765a596

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[SakodaShintaro]

Thanks! This is a good function.
LGTM