Code::contains should return true in two cases: either the given
address is within the off-heap instruction stream, or within the
trampoline's instruction stream.

This CL fixes the second case. One effect is that code printed through
the jco gdb macro again displays the builtin name correctly when given
a trampoline pc.

Drive-by: a more efficient Builtins::Lookup for embedded builtins.

Bug: v8:6666,v8:7969
Change-Id: I54f5e5881fa2aed2546b9e62aa4b9390ad21b895
Reviewed-on: https://chromium-review.googlesource.com/1146566Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54605}