JUnit Upgrade

[br648]

Checklist

• [x] Appropriate branch selected (all PRs must first be merged to dev before they can be merged to master)
• [x] Any modified or new methods or classes have helpful JavaDoc and code is thoroughly commented
• [x] The description lists all applicable issues this PR seeks to resolve
• [x] The description lists any configuration setting(s) that differ from the default settings
• [x] All tests and CI builds passing

Description

This PR aims to update JUnit from version 4 to version 5. This includes updating all JUnit references (e.g. Test, BeforeClass, Before etc), updating deprecated classes (e.g. to the org.hamcrest package) and "expect system exit" third party lib.

This PR is a prerequisite https://github.com/ibi-group/datatools-server/issues/362

[codecov-io]

Codecov Report

Merging #309 (6edaf5c) into dev (6b33a8c) will increase coverage by 0.05%. The diff coverage is n/a.

@@             Coverage Diff              @@
##                dev     #309      +/-   ##
============================================
+ Coverage     66.17%   66.23%   +0.05%     
- Complexity      926      929       +3     
============================================
  Files           136      136              
  Lines          6838     6838              
  Branches        816      816              
============================================
+ Hits           4525     4529       +4     
+ Misses         2019     2016       -3     
+ Partials        294      293       -1     

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/com/conveyal/gtfs/model/Entity.java	78.08% <0.00%> (-0.57%)	7.00% <0.00%> (ø%)
.../main/java/com/conveyal/gtfs/loader/DateField.java	73.07% <0.00%> (+7.69%)	8.00% <0.00%> (+2.00%)
src/main/java/com/conveyal/gtfs/loader/Field.java	93.93% <0.00%> (+9.09%)	23.00% <0.00%> (+1.00%)

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[br648]

@landonreed are you happy for me to merge without Evan's review?