[svg] Add feTurbulence filter (incomplete)

This was the simplest one to start with. I need to add support for the
"filter effect subregion" in order to handle tile stitching property,
so this isn't quite complete. But I believe this is enough for the
basic filters-turb-01-f test to pass, which gives us a baseline for
further filter work.

Summary of changes:
- Added attribute type and parsing for SVG integer datatype
- Added new node class for feTurbulence
- Added several new properties and parsing for feTurbulence

Bug: skia:10841
Change-Id: I8c877a5e1a837bfd527782253062eeb58febdde6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/330621
Commit-Queue: Tyler Denniston <tdenniston@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
12 files changed