Reland "webnn: Remove sync methods"

This is a reland of commit a3e84dde

This CL contains a few additional changes:
- Enables the async APIs on workers, which was causing bots to fail
  since workers could not call createContext()
- Rebaselines WPTs accordingly
- Updates the WPT expectations for the webnn-service-enabled virtual
  test suite

Original change's description:
> webnn: Remove sync methods
>
> See https://github.com/webmachinelearning/webnn/pull/548
>
> Deletes all sync methods and simplifies the names of all "Async"
> methods - e.g. BuildAsync() -> Build()
>
> Bug: 40283536, 41481333
> Change-Id: I3b38d987cb4641ea41ab9a974c46dcba16d5c108
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5292884


> Commit-Queue: Austin Sullivan <asully@chromium.org>
> Reviewed-by: Reilly Grant <reillyg@chromium.org>
> Reviewed-by: ningxin hu <ningxin.hu@intel.com>
> Reviewed-by: Alex Gough <ajgo@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1261223}

Cq-Include-Trybots: luci.chromium.try:win11-x64-fyi-rel
Bug: 40283536, 41481333, 41485898
Change-Id: Iffcb922b8175a7181deba1f4c2faa953010ae5c0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5303774


Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Austin Sullivan <asully@chromium.org>
Reviewed-by: Rafael Cintron <rafael.cintron@microsoft.com>
Reviewed-by: Alex Gough <ajgo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1262043}