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

compiler/testData/codegen/box/operatorConventions/compareTo/extensionArray.kt

@@ -7,7 +7,7 @@ fun checkLess(x: Array<Int>, y: Array<Int>) = when {
     else -> "OK"
 }
 
-fun Array<Int>.compareTo(other: Array<Int>) = size - other.size
+fun Array<Int>.compareTo(other: Array<Int>) = size() - other.size()
 
 fun box(): String {
     val a = Array<Int>(0, {0})