Upgrade to Kotlin 2.1 once all dependencies are compatible

[haukesomm]

In order to upgrade fritz2 to Kotlin version 2.1, the project's dependencies need to be updated as well.

Currently, with kotlinpoet, there is at least one imcompatible dependency as it only compiles to Kotlin 2.0.
The currently supported version can be found in their project's libs.versions.toml. Once a new compatible version has been published, we can include it in our project.

It shpuld also be investigated whether there are other incompatible versions as well.

[haukesomm]

#932 is currently blocked by this issue