When calling `Runtime.getProperties` with `accessorPropertiesOnly` we
previously did not report any private fields at all, although it is
possible to define private accessors.

Bug: chromium:1296855
Change-Id: I18b84bfc81449d224738ba3de1f0c41c234025b2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3477112
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Kim-Anh Tran <kimanh@chromium.org>
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79210}