Migrating Gradle scripts to Kotlin

[Ramazan Yapparov]

Hi Beam Dev!
I started to work on this issue 
https://issues.apache.org/jira/browse/BEAM-11589 - migrating Gradle scripts 
from Groovy to Kotlin.
Currently, I've migrated settings.gradle, buildSrc/build.gradle and 
release/build.gradle files to Kotlin.
I believe that this work should be done incrementally, so I wanted to ask if 
this amount of changes is enough for a PR or should I migrate more modules?