Deprecate/Remove TestDesigner

To clean up the Java DSL, improve the framework’s maintainability and reduce the complexity from a user´s perspective, we are going to deprecate the TestDesigner. We have been recommending the TestRunner for some time now and consider it to be more convincing than the TestDesigner. Therefore, we will migrate all Java samples to the TestRunner in the near future. This will help you to get started with a new project as well as with migration. Speaking of migration, we are planning to merge the DSL style of the TestDesigner to the TestRunner. Our goal is to get the TestRunner DSL as close as possible to the TestDesigner DSL so that the migration will not take much time. In addition, we think the TestDesigner DSL comes with some advantages and is much easier to read, write and understand. So, merging both DSL styles should make it easier for everybody to create test cases and also helps new users to understand how the framework works. In v3.0.0, the TestDesigner will finally be removed from the framework.

- [ ] #602
- [ ] #603
- [ ] #604
- [ ] #605