Handlers were recently moved to the builtins table, and we never added
full support for this flag. It doesn't add much value and lazy
deserialization is scheduled for mid-term removal anyways, so let's
just delete it.

--lazy-deserialization now controls both builtin- and
handler-deserialization behavior.

Bug: v8:6624
Change-Id: Iffb7286a00157966abf99158ba629ce4765536d6
Reviewed-on: https://chromium-review.googlesource.com/1238235
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56117}