Deprecate subarrayContentToString in order to make it internal

(cherry picked from commit 74aa0b379626d282e486ce713615e51a694c6c36)

runtime/src/main/kotlin/kotlin/collections/ArrayList.kt

@@ -160,6 +160,7 @@ actual class ArrayList<E> private constructor(
     }
 
     override fun toString(): String {
+        @Suppress("DEPRECATION")
         return array.subarrayContentToString(offset, length)
     }
 

runtime/src/main/kotlin/kotlin/collections/Arrays.kt

@@ -22,8 +22,8 @@ internal fun checkCopyOfRangeArguments(fromIndex: Int, toIndex: Int, size: Int)
 /**
  * Returns a string representation of the contents of the subarray of the specified array as if it is [List].
  */
-@SinceKotlin("1.1")
 @kotlin.internal.InlineOnly
+@Deprecated("This function will become internal soon.", level = DeprecationLevel.WARNING)
 public inline fun <T> Array<out T>.subarrayContentToString(offset: Int, length: Int): String {
     val sb = StringBuilder(2 + length * 3)
     sb.append("[")