Instead of vector-of-variant.
This:
• Makes it impossible to produce a mix of scalar variant types, which
would make no sense.
• Reduces the size of a Constant, by removing the union-tag from each
element.
Also clean up terminology. Rename 'Constant::Scalar' to
'Constant::Element'. Scalars are well-defined in WGSL, and with the
introduction of abstract-numerics, this no longer makes sense.
Bug: tint:1504
Change-Id: I599aa97ad1ea798b7db8e512a5990ba75827faad
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/91304
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>