Code object iteration was missing logic for RELATIVE_CODE_TARGET
reloc entries. Garbage collection could thus miss objects that were
referenced only as targets of pc-relative calls or jumps.

RELATIVE_CODE_TARGETs are only used on arm, mips, and s390 and only
at mksnapshot-time.

This exposed another issue in that the interpreter entry trampoline
copy we generate for profiling *did* contain relative calls in
runtime-accessible code. This is a problem, since code space on arm is,
by default, too large to be fully addressable through pc-relative
calls. This CL thus also disables the related
FLAG_interpreted_frames_native_stack feature on arm.

Drive-by: Ensure the builtins constants table does not contain Code
objects.

Bug: v8:8713,v8:6666
Change-Id: Idd914b46970ad08f9091fc72113fa7aed2732e71
Reviewed-on: https://chromium-review.googlesource.com/c/1424866Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59023}