Add a matcher API for filters in the transit service used for route lookup

[eibakke]

Summary

This change allows for a clean separation of concerns and lays the path for more efficient filtering logic down the line.

The functionality is backwards compatible, though there may be a discussion here that it should not be and that we should instead improve on some of the choices made earlier. For instance whether the longName check should really be a case insensitive prefix match.

Issue

#5630

Unit tests

Added unit tests for each matcher and the new RegularStopMatcherFactory. Also ensured that the API in local runs behaves as expected.

Documentation

Added JavaDoc.

[codecov]

Codecov Report

Attention: Patch coverage is 72.80702% with 31 lines in your changes missing coverage. Please review.

Project coverage is 69.82%. Comparing base (1030408) to head (d5d2bd5).
Report is 109 commits behind head on dev-2.x.

Files with missing lines	Patch %	Lines
...anner/apis/transmodel/TransmodelGraphQLSchema.java	42.85%	24 Missing ⚠️
...planner/transit/service/DefaultTransitService.java	0.00%	3 Missing ⚠️
...t/java/org/opentripplanner/ext/flex/FlexIndex.java	0.00%	1 Missing ⚠️
...ilter/expr/CaseInsensitiveStringPrefixMatcher.java	85.71%	1 Missing ⚠️
...nsit/model/filter/expr/NullSafeWrapperMatcher.java	85.71%	1 Missing ⚠️
...nsit/model/filter/transit/RouteMatcherFactory.java	95.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             dev-2.x    #6378      +/-   ##
=============================================
+ Coverage      69.73%   69.82%   +0.08%     
- Complexity     18024    18085      +61     
=============================================
  Files           2057     2065       +8     
  Lines          76970    77181     +211     
  Branches        7846     7852       +6     
=============================================
+ Hits           53678    53891     +213     
+ Misses         20545    20536       -9     
- Partials        2747     2754       +7     

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[leonardehrenfried]

The main code looks very neat but I have a few comments about the test code.

[t2gran]

Overall this looks very good - only one small suggestion to consider.