Also rename //modules/canvaskit/canvaskit to //modules/canvaskit/npm_build
to make it more clear the purpose of that folder (what we ship to
npm and stage our builds for local testing).
Bug: skia:11203
Change-Id: I4299ded97d14f4155c36798d60e88a660ce6fe6a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/372392
Reviewed-by: Kevin Lubick <kjlubick@google.com>
