[webgpu cts] prefix failure message with test query

This will help LUCI Analysis cluster test failures instead of grouping
multiple tests under the same cluster of "Array had unexpected
contents..."

Change-Id: I2a726330ee85843fce991eb3c7b276d012e7f3a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4980179
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Auto-Submit: Austin Eng <enga@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1215764}