[canvaskit] Clean up Shader docs/types/names

There should be no functional changes.

I also address some forgotten changes to canvaskit-wasm-tests.ts
from CLs last week.

Bug: skia:10717
Change-Id: If02f60813af0aa42acd637639e40f4d6d0b38bd7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/327157
Reviewed-by: Nathaniel Nifong <nifong@google.com>
8 files changed