Support for Kotlin 2.0 and beyond

[alllex]

Kotlin 2.0 was released almost a year ago, yet the latest version of Kotlin supported by the notebook is 1.9.23.

The documentation for Kotlin Notebooks says that the notebooks are a great way to explore APIs, yet we don't have an option to explore new Kotlin Standard library APIs this way.

[cmelchior]

Hi. Work on bumping the Language Version to 2.1 is underway and is close to being complete. You can follow the progress in this meta issue : https://youtrack.jetbrains.com/issue/KTNB-891/Update-Kotlin-Jupyter-Kernel-to-K2-REPL-implementation