This is the first step in unifying the way decorations are parsed - i.e. instead of parsing decorations in different ways based on the predicted grammar that follows, we can parse decorations blocks in a unified way, then later verify what we have is as expected.
`StructDecoration` has been transformed from an `enum class` to a proper class so it can derive from `Decoration`.
Bug: tint:282
Bug: tint:291
Change-Id: Iaf12d266068d03edf695acdf2cd21e6cc3ea8eb3
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/31663
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>
Ben Clayton