[K/N][build] Composite build with build.tools-conventions plugin

Adds convention plugin instead of sources inclusion
inside the buildSrc, effectively reducing the amount
of the code to be compiled in buildSrc.

Merge-request: KT-MR-8898

kotlin-native/backend.native/build.gradle

@@ -13,7 +13,7 @@ buildscript {
 
 apply plugin: 'java'
 apply plugin: 'kotlin'
-apply plugin: org.jetbrains.kotlin.NativeInteropPlugin
+apply plugin: "native-interop-plugin"
 apply plugin: "maven-publish"
 apply plugin: CppConsumerPlugin