Move patheffect details to (private) base subclass

bug: skia:11957
Change-Id: Iceaa0ac1d7a3f049d2725629d78c755ad03a2862
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/411302
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
23 files changed