Even though both are allowed in the style guide, it recommends to use
'using', as its syntax is more consistent with the rest of C++.
This CL turns all typedefs in wasm code to 'using' declarations.

R=ahaas@chromium.org

Bug: v8:8834
Change-Id: Ibdce88a5cc31e0785cbc1b34088bd39aa3ec84b3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1545890Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60519}