Update docs and samplecode to use new image filter factories

Bug: skia:9280
Change-Id: I03ba9bf1cc952dec77664721fdb3a311f47f7e89
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/230884
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Hal Canary <halcanary@google.com>
12 files changed