fix(autoware_pointcloud_preprocessor): fix cppcheck warnings of functionStatic

[taisa1]

Description

This is a fix based on cppcheck warning functionStatic.

sensing/autoware_pointcloud_preprocessor/src/downsample_filter/robin_hood.h:570:8: performance: inconclusive: Technically the member function 'robin_hood::detail::NodeAllocator::addOrFree' can be static (but you may consider moving to unnamed namespace). [functionStatic]
sensing/autoware_pointcloud_preprocessor/src/downsample_filter/robin_hood.h:1054:10: performance: inconclusive: Technically the member function 'robin_hood::detail::Table::DataNode::destroy' can be static (but you may consider moving to unnamed namespace). [functionStatic]
sensing/autoware_pointcloud_preprocessor/src/downsample_filter/robin_hood.h:1055:10: performance: inconclusive: Technically the member function 'robin_hood::detail::Table::DataNode::destroyDoNotDeallocate' can be static (but you may consider moving to unnamed namespace). [functionStatic]
sensing/autoware_pointcloud_preprocessor/src/downsample_filter/robin_hood.h:1265:10: performance: inconclusive: Technically the member function 'robin_hood::detail::Table::Destroyer::nodes' can be static (but you may consider moving to unnamed namespace). [functionStatic]
sensing/autoware_pointcloud_preprocessor/src/downsample_filter/robin_hood.h:1267:10: performance: inconclusive: Technically the member function 'robin_hood::detail::Table::Destroyer::nodesDoNotDeallocate' can be static (but you may consider moving to unnamed namespace). [functionStatic]
sensing/autoware_pointcloud_preprocessor/src/downsample_filter/robin_hood.h:1273:10: performance: inconclusive: Technically the member function 'robin_hood::detail::Table::Destroyer::nodes' can be static (but you may consider moving to unnamed namespace). [functionStatic]
sensing/autoware_pointcloud_preprocessor/src/downsample_filter/robin_hood.h:1288:10: performance: inconclusive: Technically the member function 'robin_hood::detail::Table::Destroyer::nodesDoNotDeallocate' can be static (but you may consider moving to unnamed namespace). [functionStatic]

Static member functions cannot be const, so some const are removed.

Related links

C++ reference (static)

How was this PR tested?

Only checked if build succeeded.

Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 29.29%. Comparing base (ca32505) to head (877461e).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8163      +/-   ##
==========================================
- Coverage   29.31%   29.29%   -0.02%     
==========================================
  Files        1609     1646      +37     
  Lines      119413   120871    +1458     
  Branches    51480    52271     +791     
==========================================
+ Hits        35002    35413     +411     
- Misses      75111    76051     +940     
- Partials     9300     9407     +107     

Flag	Coverage Δ		*Carryforward flag
differential	15.00% <ø> (?)
total	29.14% <ø> (-0.17%)	⬇️	Carriedforward from a1c77e7

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[atsushi421]

LGTM