Fix entrances being removed from walk steps

[HenrikSundell]

Summary

Prevents removing of walksteps with entrance information

Issue

Closes #6528

Unit tests

Write a few words on how the new code is tested.

Documentation

Changelog

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Bumping the serialization version id

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 70.27%. Comparing base (9807f18) to head (21dbabe).
Report is 243 commits behind head on dev-2.x.

Files with missing lines	Patch %	Lines
...ing/algorithm/mapping/StatesToWalkStepsMapper.java	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             dev-2.x    #6530      +/-   ##
=============================================
+ Coverage      70.18%   70.27%   +0.08%     
- Complexity     18310    18393      +83     
=============================================
  Files           2082     2088       +6     
  Lines          77195    77416     +221     
  Branches        7827     7841      +14     
=============================================
+ Hits           54177    54401     +224     
+ Misses         20251    20246       -5     
- Partials        2767     2769       +2     

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[leonardehrenfried]

Please add a test in StatesToWalkStepsMapperTest. You probably also have to update support for it in the TestStationBuilder.

[vesameskanen]

These changes fix the entrance problems with HSL data.

Overall logic in this class is difficult to grasp, but I guess refactoring it all is not in the scope of this PR.