[repo] Migrate ideaRtHack.gradle.kts into convention plugin

Otherwise, it could not find methods from buildsrc-compat.

gradle/ideaRtHack.gradle.kts

@@ -1,23 +0,0 @@
-// Remove this hack when IDEA-285445 (Gradle plugin doesn't handle java-rt from IDEA maven repo the same way as idea_rt.jar) is fixed
-// https://github.com/JetBrains/intellij-community/blob/0e2aa4030ee763c9b0c828f0b5119f4cdcc66f35/plugins/gradle/java/resources/org/jetbrains/plugins/gradle/java/addTestListener.groovy#L11
-if (isIdeaActive) {
-    gradle.taskGraph.whenReady {
-        allTasks.filterIsInstance<Test>().forEach { task ->
-            task.doFirst {
-                task.classpath.files.find { it.name.startsWith("java-rt") }?.let { javaRtJar ->
-                    try {
-                        val urlClassLoader =
-                            Class.forName("org.gradle.launcher.daemon.bootstrap.DaemonMain").classLoader as? java.net.URLClassLoader
-
-                        urlClassLoader?.let {
-                            it::class.java.getMethod("addURL", java.net.URL::class.java)
-                                .invoke(it, javaRtJar.toURI().toURL())
-                        }
-                    } catch (e: RuntimeException) {
-                        logger.log(LogLevel.WARN, "Failed to load java-rt into Gradle daemon", e)
-                    }
-                }
-            }
-        }
-    }
-}