Don't create runnable platform jars anymore, since all they really do is increase build time. Also fix texts and Gradle deprecations. Also also publish common with its shadowed configuration, not the plain java components.
* Make use of `TYPESAFE_PROJECT_ACCESSORS` and `VERSION_CATALOGS` Gradle feature previews to clean up build scripts
* Bump setup-java action to v2, specify AdoptOpenJDK distribution
This does not affect any previous states of this project; only future modifications as well as the project as a whole will be under the GNU General Public License from now on. The newly introduced api directory, partly split from common, is an exception to this, still being licensed under the MIT license.
See the README for details.
