This CL adds const-eval for the `inverseSqrt` builtin.
Bug: tint:1581
Change-Id: Ieef063416a8033b5fac9396e30c76c20b3360a90
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/111581
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>