When moving arguments for calls into the right registers and stack
slots, we were sometimes overwriting stack slots which would still be
used later to load arguments from. This is because we popped the (wasm)
value stack before executing the register moves, hence the stack
transfer would think the values are not being used any more and reuse
the stack slots.
With this CL, we only pop the arguments from the stack after executing
the stack transfer.

R=ahaas@chromium.org

Bug: v8:7366, v8:6600
Change-Id: I3aa5126c82634fd281959075e91e73465c39abaa
Reviewed-on: https://chromium-review.googlesource.com/883802
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50853}