FeedbackVector and AllocationSite are now NeverReadOnlySpaceObjects

Bug: v8:7786
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I6109c0c4a391b19c5c77c61b52aae989707fecc4
Reviewed-on: https://chromium-review.googlesource.com/1120532
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54139}