Make Array.indices extension property, move to stdlib

This is not something that needs to be intrinsified. Note that compiler
optimizations are still possible and the fact whether 'indices' is a member or
an extension is irrelevant to the optimizer

core/runtime.jvm/src/kotlin/jvm/internal/Intrinsics.java

@@ -19,6 +19,7 @@ package kotlin.jvm.internal;
 import kotlin.IntRange;
 import kotlin.KotlinNullPointerException;
 
+import java.lang.Deprecated;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashSet;
@@ -93,6 +94,8 @@ public class Intrinsics {
         return first == null ? second == null : first.equals(second);
     }
 
+    // This method is not used from generated code anymore but kept for backwards compatibility
+    @Deprecated
     public static IntRange arrayIndices(int length) {
         return new IntRange(0, length - 1);
     }