Before, we were redirecting each function to the interpreter by iterating all
code and patching all call sites using this one function. The runtime was
hence quadratic if all functions were redirected to the interpreter as
done by the --wasm-interpret-all flag.
This CL fixes this to only iterate the code once and redirecting an
arbitrary number of function.

R=ahaas@chromium.org, titzer@chromium.org
BUG=v8:5822

Change-Id: Ia4f2e94a2468f9bef3035b599e1f8a18acf309da
Reviewed-on: https://chromium-review.googlesource.com/455785
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43946}