Migrate korro to 0.2.1

[AndreiKingsley]

Update korro version to 0.2.0 and migrate.

[Jolanrensen]

We can already bump to 0.1.7 with the fix from @Allex-Nik
but for 0.2.x, we should likely wait for the next version due to:

Only fun declarations are valid FUN/FUNS targets. Properties, classes, top-level expressions, and .kts scripts now produce a diagnostic.

and #1703, which uses that mechanism. Already contacted @devcrocod about it :)

[devcrocod]

published korro 0.2.1: https://plugins.gradle.org/plugin/io.github.devcrocod.korro
used KtNamedDeclaration instead of KtNamedFunction