Fix bazel Dawn build

Dawn moved these files to src/utils in:
https://dawn-review.git.corp.google.com/c/dawn/+/312837

Change-Id: Ifaad0cbfd364027bf7ec5c609fe3608407e010f5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1253417
Reviewed-by: Nicolette Prevost <nicolettep@google.com>
Reviewed-by: Kaylee Lubick <kjlubick@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>