[K/N] Move kotlin.native.internal.GC into kotlin.native.runtime

As a part of efforts to stabilize Native stdlib #KT-55765.

kotlin-native/performance/ring/src/main/kotlin-native/cleanup.kt

@@ -1,5 +1,6 @@
 package org.jetbrains.ring
 
-import kotlin.native.internal.GC
+import kotlin.native.runtime.GC
 
+@OptIn(kotlin.native.runtime.NativeRuntimeApi::class)
 actual fun cleanup() { GC.collect() }

kotlin-native/performance/ring/src/main/kotlin/org/jetbrains/ring/WeakRefBenchmark.kt

@@ -5,7 +5,7 @@
 
 package org.jetbrains.ring
 
-import kotlin.native.internal.GC
+import kotlin.native.runtime.GC
 import kotlin.native.ref.WeakReference
 import kotlin.test.assertEquals
 import kotlin.test.assertNotEquals
@@ -46,6 +46,7 @@ private fun ReferenceWrapper.stress() = (1..REPEAT_COUNT).sumOf {
     this.value
 }
 
+@file:OptIn(kotlin.native.runtime.NativeRuntimeApi::class)
 open class WeakRefBenchmark {
     private val aliveRef = ReferenceWrapper.create()
     private val deadRef = ReferenceWrapper.create().apply {