This adds Code::has_foo() and Code::foo_size() helpers for inlined
metadata sections (currently: the safepoint table, handler table,
constant pool, and code comments). Prior to this, each call site had
to know implementation details of the instruction area layout.

Bug: v8:8758
Change-Id: I9dc391992a4bf709ee403beab8606d85540dc1be
Reviewed-on: https://chromium-review.googlesource.com/c/1451838
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59357}