Rework clustering logic for sandbox geocoder

[leonardehrenfried]

Summary

OTP's geocoder is an important part of IBI's deployments and many customers like its specificity and customisability. During several rounds of feedback it was requested that the clustering feature be changed so that all elements in a cluster can be independently found. For this reason information that used to be hidden (primary, secondary elements) are now returned in the API.

This will allow the frontend components to build customised UIs for each customer.

⚠️ If you're a user of the cluster geocoding API, this is a breaking change!

cc @miles-grant-ibigroup

[codecov]

Codecov Report

Attention: Patch coverage is 98.09524% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 68.49%. Comparing base (8f632f1) to head (6a73f01).
Report is 26 commits behind head on dev-2.x.

Files	Patch %	Lines
...pentripplanner/ext/geocoder/StopClusterMapper.java	96.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             dev-2.x    #5879      +/-   ##
=============================================
+ Coverage      68.47%   68.49%   +0.02%     
- Complexity     16698    16709      +11     
=============================================
  Files           1914     1916       +2     
  Lines          72673    72702      +29     
  Branches        7454     7449       -5     
=============================================
+ Hits           49763    49800      +37     
+ Misses         20340    20336       -4     
+ Partials        2570     2566       -4     

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[binh-dam-ibigroup]

Approving with a few minor tweaks. Code looks solid.