[canvaskit] Remove Sk from nearly all function/type names.

This is a massive breaking change for all existing users of CanvasKit.

It will be (one of the only) changes in 0.19.0 to make the transition
easier.

Suggested reviewing order:
 - index.d.ts (to see type changes). Notice SkPicture still has Sk
   prefix, but no other types do (this felt "right" since Sk is
   part of the name of the type, but I can be swayed on this).
 - canvaskit-wasm-tests.ts
 - tests/*.spec.js
 - interface.js and helper.js
 - html examples
 - markdown files

Change-Id: I3b3d3815df2078f986893df3c70101d6248c117d
Docs-Preview: https://skia.org/?cl=322617
Bug: skia:10717
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/322617
Commit-Queue: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Nathaniel Nifong <nifong@google.com>
46 files changed