[K/N][kotlin.test] Make GeneratedSuites public

Issue #KT-47915 fixed

kotlin-native/runtime/src/main/kotlin/kotlin/native/internal/test/Launcher.kt

@@ -3,13 +3,21 @@
  * that can be found in the LICENSE file.
  */
 
+@file:OptIn(ExperimentalStdlibApi::class)
+
 package kotlin.native.internal.test
 
 import kotlin.system.exitProcess
 import kotlin.native.concurrent.*
 
+// Advanced users may need an access to test suites generated by the compiler to integrate
+// our test machinery with third party test runners (e.g. with xctestrun).
+// So we keep this object public but protect it with @ExperimentalStdlibApi
+// to stress that it is not a part of the stable API.
+// Related YT issue: KT-47915.
+@ExperimentalStdlibApi
 @ThreadLocal
-private object GeneratedSuites {
+public object GeneratedSuites {
    val suites = mutableListOf<TestSuite>()
    fun add(suite: TestSuite) = suites.add(suite)
 }