This gathers TurboFan compilation statistics for WebAssembly separately
from the JavaScript statistics. It is a preparation to having multiple
Isolates trigger TurboFan compilations in a shared engine. By adding
compilation statistics to the engine, their lifetime is independent of
any particular Isolate.

R=ahaas@chromium.org

Change-Id: I1bd0fbe6d6bde65ca813ccfd1154558ea6cddb07
Reviewed-on: https://chromium-review.googlesource.com/1131121
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54357}