This patch allows the deoptimizer to keep embedded pointers intact.
Previously, the deoptimizer had to clear embedded pointers because
the mark-compactor relied on the Code::marked_for_deoptimization flag
to indicate whether the embedder pointers were cleared or not.

This patch adds a new flag called Code::embedded_objects_cleared()
and thus can correctly clear dead weak objects in deoptimized code.

Bug: v8:8459
Change-Id: I6eb6ff3aa2182bc41730e0a249965f8d8c0525ce
Reviewed-on: https://chromium-review.googlesource.com/c/1335943Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57584}