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}