Remove test and tools

The end to end tests in `./test/**` are already tested im the Dawn repo.
There's no need to maintain another copy of these files in Tint.
Reduces repo size.

Remove tools.
These were to aid in development, but development is now done in Dawn.

Bug: dawn:1339
Change-Id: I0b677e8e4e9bb9156e8a42f83a2064172a5eaa97
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/86521
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Ben Clayton <bclayton@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>