The return value of {memory_copy_wrapper} was defined as {bool} in
the original CL. When compiled with clang, the full return register is
written when {true} or {false} is returned. With msvc, however, the
return value is written as a single byte, without zero-extension. In
generated code, the full return register is used and therefore stale
bytes in the return register caused problems.

With this CL the return value is changed to {uint32_t}. This enforces
zero-extension of the return value and thereby fixes the issue.

R=clemensb@chromium.org

Bug: v8:10281
Change-Id: I628d01cfd7193fa960a7ccdf0d9fd896f510cd3e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2096626
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66666}