tint: Rename 'type' to 'alias'
Bug: tint:1812
Change-Id: I50bd8b036b47b4ec223a81eda53bd658d19645e9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/117211
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>