Use @Nested classes instead of comments for grouping tests

[bvkatwijk]

JUnit Jupiter, tests can be grouped using Nested classes

@Nested tests give the test writer more capabilities to express the relationship among several groups of tests. Such nested tests make use of Java’s nested classes and facilitate hierarchical thinking about the test structure

This seems to fit the exact purpose of the -- comment divisors in test., and enables a number of useful features like being able to run the set of nested tests individually.

[bvkatwijk]

I have some time to contribute to open source projects - let me know if this is something I could pick up 👍

[pivovarit]

Sure thing :) just please target version/0.x first

[pivovarit]

A quick heads up: https://github.com/orgs/vavr-io/discussions/2953

version/0.x will be becoming the new main branch - no worries, I will backport your changes