The counters are the last use of the Isolate. Remove it by passing in
the counters in a shared_ptr. This way, we can also refactor the
counters later to be per engine or per process.
In a follow-up CL, we can then remove the Isolate, the foreground task
runner and the cancellable task manager from the compilation state.

R=mstarzinger@chromium.org

Bug: v8:8689, v8:8050
Change-Id: I66b4fab77f770cb8a5463244054b428eef1b7c61
Reviewed-on: https://chromium-review.googlesource.com/c/1451922
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59339}