Exceptions were detected by checking for a pending exception on the
isolate, but {CallWasmFunctionForTesting} was clearing any pending
exception before returning.
This CL fixes that by explicitly passing back a boolean which is set if
an exception occurred during execution.

R=ahaas@chromium.org

Bug: chromium:1115280
Change-Id: Ife71ceef0751d18e0870335b9520c2bf77e351cc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2352787Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69404}