Update is_compiled() and has_feedback_vector() to return false in the case
where the SFI's bytecode has been flushed, but the JSFunction hasn't yet been
reset to uncompiled. Also add code to reset the JSFunction when it is recompiled
lazily.

BUG=v8:8394

Change-Id: I7c5f79066603ac1ae097a0a62c625b1a8e39431c
Reviewed-on: https://chromium-review.googlesource.com/c/1363138Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58148}