webnn: run WPT WebNN API conformance tests by each context options
This CL uses variant[1] to test WPT WebNN API conformance tests by CPU
and GPU devices, removes duplicated test files of gpu folder, and
updates expected results files.
[1] https://web-platform-tests.org/writing-tests/testharness.html#variants
Bug: 331489772
Change-Id: Ic907a84fa643e062cb838220dc3a33ea739791dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5402035
Reviewed-by: Reilly Grant reillyg@chromium.org
Reviewed-by: David Baron dbaron@chromium.org
Commit-Queue: Reilly Grant reillyg@chromium.org
Reviewed-by: Austin Sullivan asully@chromium.org
Cr-Commit-Position: refs/heads/main@{#1294489}