Simplify Kotlin bootstrap application in the project

Move all the code to apply Kotlin bootstrap into settings script plugin
which does following:
- configures based either on the repo root 'local.properties' or on the
root project gradle properties or on the repo root 'gradle.properties'
current type of bootstrap
- automatically adds Kotlin bootstrap repository with
exclusive content, so bootstrap dependencies will not be by mistake
downloaded from other repository
- automatically forces all Kotlin plugins applied in the build to use
bootstrap version

This script should be applied only in project settings.gradle and then
it does all the configuration by itself.

repo/scripts/Readme.md

@@ -3,3 +3,4 @@
 This directory contains the scripts that should be applied before even settings evaluation
 and cannot be convention plugins:
 - [script](cache-redirector.settings.gradle.kts) to redirect all repositories to cache redirector service
+- [script](kotlin-bootstrap.settings.gradle.kts) to apply Kotlin bootstrap settings