This CL adds const-eval for the `acos` builtin.
Bug: tint:1581
Change-Id: I01c0f48e73eedf87cf9c912715487f8eea44f64e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/108341
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>