Now that all validation has been moved to the Resolver, we can delete
the Validator. This change removes everything except validator.h with
the public no-op API. We can remove this once we remove dependencies on
this public API in Dawn.
Bug: tint:642
Change-Id: I644cd900615509c9cdd57c375c6217a50126e36c
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/47023
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>