For unknown reasons, WasmInterpreterInternals was a zone object. However
WasmInterpreterInternals indirectly owns a global handle and a
unique_ptr, both for the interpreter stack. As a zone object,
WasmInterpreterInternals is never destructed, and therefore never frees
the unique_ptr. With this CL I make WasmInterpreterInternals a normal
object and allocate it into a unique_ptr, so that it gets destructed
properly.

R=mstarzinger@chromium.org

Bug: chromium:1000610
Change-Id: Ie08c5627393a434521f5c32702bf9945db2c7811
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1807361Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63835}