Allow "iterative" finalization when off-thread finalization is enabled,
meaning that each compiled function is finalized immediately after
compilation, rather than all functions being first compiled and then
finalized.

This is what we do on the main thread, and it reduces peak Zone memory
usage by being able to discard empty compilation Zones earlier.

One necessary functionality for this was being able to defer the
finalization of asm.js functions until the main thread pause, since
they can't be finalized off-thread -- previously we would just bail
out of doing the off-thread finalization if any inner function was
asm.js.

Bug: chromium:1011762
Change-Id: I21ff69d62eaa93b5ff908624b7115601e36f70f1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2282536Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69032}