Revert "webnn: Remove sync methods"

This reverts commit a3e84dde.

Reason for revert: One Win 11 , blink_wpt_tests are failing consistently since https://ci.chromium.org/ui/p/chromium/builders/ci/Win11%20Tests%20x64/19453/blamelist This CL seems to be a candidate for causing this.

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}

Bug: 40283536, 41481333
Change-Id: Ib59afe686ae8e18bcad63ff7d15816cd93090f00
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5301381
Owners-Override: Markus Heintz <markusheintz@google.com>
Auto-Submit: Markus Heintz <markusheintz@google.com>
Commit-Queue: Markus Heintz <markusheintz@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1261576}