Other WebAssembly tools like wabt and wasmparser ignore empty strings
for local variable and parameter names, and just generate their own
names for it. Update V8 to comply with this convention.

Bug: chromium:1134531
Change-Id: Ic724482d93398feaf6b0797eec5a55f8ca508ca5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2448457Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Kim-Anh Tran <kimanh@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70305}