[CALCITE-2457] JUnit4 -> JUnit5

[vlsi]

Checklist:

• @Test
• Code style (e.g. line length after migration)
• Assert
• @Parameterized
• Assume

Out of scope: cassandra, mongodb, elasticsearch, geode, linq4j (see junit4=true in gradle.properties)

This removes JUnit4 from most of the modules, so there will be less confusion between @Test annotations.

[asereda-gs]

Is string/replace still necessary if most of the tests are migrated already ?

[vlsi]

I think we can drop that later.

The use case is as follows:

1. You drop junit4=true from mongodb/gradle.properties, and execute ./gradlew spotlessApply. It would use the replacements to automatically replace the bits in mongodb module.

2. When somebody implemented JUnit4-based test, then they rebase on top of master.
   The replacement rules would convert the code to the new format automatically!
   That is nice, isn't it?

[vlsi]

Unfortunately, assertEquals, assertTrue, and frields have different APIs between 4 and 5, so they can't be converted with a regexp :-(

[asereda-gs]

@vlsi does it make sense to squash commits ? There is no much information in intermediate changes.

[vlsi]

I think it helps to review the changes. For instance, mechanical edits like "alter package names" are not that interesting, and it is even hard to view in GitHub UI.

We have 3700+ commits, so 7 vs 1 won't make a difference.