Change type elements kind in empty array boilerplate desc from PACKED_ELEMENTS...

Change type elements kind in empty array boilerplate desc from PACKED_ELEMENTS to PACKED_SMI_ELEMENTS

The default array elements kind should be PACKED_SMI_ELEMENTS (top of type lattice)  to allow type
transitions to other types.

Change-Id: Icda969d0553628ef75d6c26bf6f32fef46512f0f
Reviewed-on: https://chromium-review.googlesource.com/1188133Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Chandan Reddy <chandanreddy@google.com>
Cr-Commit-Position: refs/heads/master@{#55382}

src/heap/setup-heap-internal.cc

@@ -532,7 +532,7 @@ bool Heap::CreateInitialMaps() {
     ArrayBoilerplateDescription::cast(obj)->set_constant_elements(
         roots.empty_fixed_array());
     ArrayBoilerplateDescription::cast(obj)->set_elements_kind(
-        ElementsKind::PACKED_ELEMENTS);
+        ElementsKind::PACKED_SMI_ELEMENTS);
   }
   set_empty_array_boilerplate_description(
       ArrayBoilerplateDescription::cast(obj));