Development: Enforce consistent usage of nullness annotations

[Strohgelaender]

Checklist

General

• This is a small issue that I tested locally and was confirmed by another developer on a test server.
• Language: I followed the guidelines for inclusive, diversity-sensitive, and appreciative language.
• I chose a title conforming to the naming conventions for pull requests.

Motivation and Context

There are many possibilites for defining nullness annotations in Java (see https://stackoverflow.com/questions/4963300/which-notnull-java-annotation-should-i-use).

We decided for Artemis to use javax.validation.constraints.NotNull and javax.annotation.Nullable (see #6019)

Description

This PR adds an ArchUnit test that verifies the correct annotations. Since ArchUnit defines simple name matcher only for classes and not for Annotations, I implemented them myself.

Steps for Testing

code review

Review Progress

Code Review

• Code Review 1
• Code Review 2

[tobias-lippert]

Code LGTM, thanks for adding the ArchUnit test to avoid regressions.

[DominikRemo]

Code LGTM 🚀