Fix junit version

[chris-ch]

Along with junit version upgraded to 4.13 (gradle test was failing) and hamcrest updated to 3.0, added Codespace config for easier dev onboarding.

[Bombe]

Latest JUnit version is 4.13.2. Any particular reason you’re not updating to the latest version?

[Bombe]

Hamcrest isn’t being split up anymore. Both org.hamcrest:hamcrest-library and org.hamcrest:hamcrest-core are now basically empty JAR files that both depend on org.hamcrest:hamcrest in order to get Maven and Gradle to do the right thing. We should cut out the middleman here.

[Bombe]

Hmm, what branch did you base your pull request on? My gradle/verification-metadata.xml already contains keys for both hamcrest and JUnit…

[Bombe]

Settings for your local IDE do not belong in version control.

[Bombe]

This does not belong in this pull request.

[Bombe]

This also looks quite unrelated. Please don’t mix unrelated features in pull requests, that just makes it more confusing and more complicated to get anything done.

[chris-ch]

I re-forked the project, starting from scratch completely and from the "next" branch, the jar build is working:

$ ./gradlew jar

But then the tests fail:

@chris-ch ➜ /workspaces/fred (next) $ ./gradlew --parallel test

> Task :compileTestJava FAILED
/workspaces/fred/test/freenet/client/filter/TheoraBitstreamFilterTest.java:12: error: cannot find symbol
import static org.junit.Assert.assertThrows;
^
  symbol:   static assertThrows
  location: class Assert
/workspaces/fred/test/freenet/support/api/BooleanCallbackTest.java:4: error: cannot find symbol
import static org.junit.Assert.assertThrows;
^
  symbol:   static assertThrows
  location: class Assert
/workspaces/fred/test/freenet/support/SimpleFieldSetTest.java:20: error: cannot find symbol
import static org.hamcrest.Matchers.anEmptyMap;
^
  symbol:   static anEmptyMap
  location: class Matchers
...

Creating another PR dedicated to that.