Make GraphQLIntegrationTest less flaky

[leonardehrenfried]

Summary

Since last week we have seen some flaky tests which are due to #5480.

Example: https://github.com/opentripplanner/OpenTripPlanner/actions/runs/6765951122/job/18386315013#step:5:5932

Often it is solved by re-running the tests, which is quite annoying.

This PR attempts to fix it by re-creating new stops which hopefully have an index that is in sync with the current state of StopLocation.INDEX_COUNTER. It's just papering over the problem so we need a proper fix for that.

Issue

Relates to #5480

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (35ebd1a) 66.78% compared to head (57e54bd) 66.80%.
Report is 5 commits behind head on dev-2.x.

Additional details and impacted files

@@              Coverage Diff              @@
##             dev-2.x    #5481      +/-   ##
=============================================
+ Coverage      66.78%   66.80%   +0.02%     
  Complexity     15558    15558              
=============================================
  Files           1806     1806              
  Lines          69842    69822      -20     
  Branches        7357     7357              
=============================================
+ Hits           46643    46647       +4     
+ Misses         20740    20718      -22     
+ Partials        2459     2457       -2     

Files	Coverage Δ
...pentripplanner/transit/service/StopModelIndex.java	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes

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