In particular, remove {toUint8Array} method and make {toBuffer} return
a {Uint8Array} view to the buffer like before
https://crrev.com/c/1508352. Also, the returned view does not need to be
another copy of the bytes, it can really just be a view.

As a follow-up, this requires the test-only DeserializeWasmModule
runtime method to receive the wire bytes as Uint8Array, and also
requires the {IsWasmCompileAllowed} callback to handle
{ArrayBufferView} (like chromium's version already does).

R=ahaas@chromium.org

Change-Id: I87296cdbac14b74e7c8b38a372aa3df572ca6ad6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1518172
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60195}