Make Array.size() a function instead of a property

Also add a deprecated extension property to help migration. This is done to
unify getting size of arrays and collections

core/builtins/native/kotlin/Array.kt

@@ -16,10 +16,12 @@
 
 package kotlin
 
-public class Array<reified T>(public val size: Int, init: (Int) -> T) : Cloneable {
+public class Array<reified T>(size: Int, init: (Int) -> T) : Cloneable {
     public fun get(index: Int): T
     public fun set(index: Int, value: T): Unit
 
+    public fun size(): Int
+
     public fun iterator(): Iterator<T>
 
     public val indices: IntRange