Add result.List.StatusTree() for building a query.Tree[Status].
Add helpers for serializing results.
Add helpers for merging and de-duplicating results.
Change the interface of result.List.ReplaceDuplicates() so that the
merging function takes a status set instead of a list of results.
Bug: dawn:1342
Change-Id: I77580ec5fd4c8f12109fb6e9e83afea8b740260c
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/87240
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>