Const-qualified fields are allowed in both classes and structs.
In both cases, const fields can only be set via initialization
during construction.

Drive-by: unitialized -> uninitialized

Bug: v8:7793
Change-Id: Idec08df30f7897c756b7dd6f2b10bb6012fefb6a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1547853
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60592}