[SVG] merge SVGAnimatedNewPropertyAnimator to SVGAnimatedTypeAnimator

After the new svg properties transition, SVGAnimatedNewPropertyAnimator is the only SVGAnimatedTypeAnimator.
This CL merges the SVGAnimatedNewPropertyAnimator functionality to SVGAnimatedTypeAnimator, and removes SVGAnimatorFactory.

BUG=349370

Review URL: https://codereview.chromium.org/194623002

git-svn-id: svn://svn.chromium.org/blink/trunk@169010 bbb929c8-8fbe-4397-9dbb-9b2b20218538