The compilation state of a native module is now extracted into its own
datastructure. It reflects which functions are left to compile, and contains
task managers to accomplish parallel and asynchronous compilation.

Bug: 
Change-Id: I45308c7b32ba78e6c83f2d260990846a653bbd9c
Reviewed-on: https://chromium-review.googlesource.com/958865
Commit-Queue: Kim-Anh Tran <kimanh@google.com>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52013}