With the updated WGSL grammar the `@align` attribute takes an
expression instead of a value. This CL updates the internal data
structures to store an expression instead of an integer value.
The parser still only parses integers, they're just turned into
`IntLiteralExpressions` at the moment.
Bug: tint:1633
Change-Id: If34901798ed6ceaced354bc06ae9b6df875b700e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/99980
Reviewed-by: Ben Clayton <bclayton@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
4964d9bc20