There is no good reason to have the meat of most objects' initialization
logic in heap.cc, all wrapped by the CALL_HEAP_FUNCTION macro. Instead,
this CL changes the protocol between Heap and Factory to be AllocateRaw,
and all object initialization work after (possibly retried) successful
raw allocation happens in the Factory.

This saves about 20KB of binary size on x64.

Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: Icbfdc4266d7be8b48d2fe085f03411743dc6a0ca
Reviewed-on: https://chromium-review.googlesource.com/959533
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52416}