[build] Fix weird dependencies management

kotlin-gradle-plugin-integration-tests on runtime uses relocated
compiler jars. A special handling is required to support this.

Looks like 'kotlin-gradle-plugin-test-utils' was meant to help
here somehow, but was accidentally broken at some point. It went
unnoticed because not much classes from transitive dependencies
of 'kotlin-gradle-plugin-test-utils' were used.

The change in this commit still leaves a few questions about this
configuration, but at leats it makes it possible to use compiler
classes (e.g. KotlinTestUtils)

libraries/tools/kotlin-gradle-plugin-test-utils-embeddable/build.gradle.kts

@@ -21,6 +21,8 @@ dependencies {
         api(projectTests(projectName)) { isTransitive = false }
         embedded(projectTests(projectName)) { isTransitive = false }
     }
+
+    embedded(intellijJavaRt())
 }
 
 runtimeJar(rewriteDefaultJarDepsToShadedCompiler())