StoreHandlers can store either a Code object or a Smi, so the
smi_handler field on DataHandler is a Code|Smi. But, LoadHandlers can
only store Smis here so add a shadowing smi_handler definition which
only allows / returns Smis.

Change-Id: Icc1c508db268950990b9c84b9e682b9a9b1f43e5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3663745
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80775}