The wasm/ directory is inconsistent in many places, often within the
same file. For all code that exists in a v8::internal::wasm namespace,
this CL removes any wasm:: qualifiers, which is especially helpful
since most types are already Wasm-named, such as WasmCode, WasmModule,
etc. Namespace qualifiers are redundant inside the wasm:: namespace and
thus go against the main point of using namespaces. Removing the
qualifiers for non Wasm-named classes also makes the code somewhat more
future-proof, should we move some things that are not really WASM-specific
(such as ErrorThrower and Decoder) into a higher namespace.

R=clemensh@chromium.org,mstarzinger@chromium.org

Change-Id: Ibff3e1e93c64c12dcb53c46c03d1bfb2fb0b7586
Reviewed-on: https://chromium-review.googlesource.com/1160232
Commit-Queue: Ben Titzer <titzer@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54862}