Shadow Gradle plugin 3rd party dependencies

Such dependencies will be embedded into plugin jar and their package
will be relocated. This is need to avoid dependency conflicts with
user build scripts dependencies or other Gradle plugins.

Kotlin project dependencies are not shadowed.

^KT-46034 Fixed

plugins/atomicfu/atomicfu-compiler/build.gradle.kts

@@ -7,7 +7,6 @@ description = "Atomicfu Compiler Plugin"
 plugins {
     kotlin("jvm")
     id("jps-compatible")
-    id("de.undercouch.download")
 }
 
 val antLauncherJar by configurations.creating