[SVG] refactor determineAnimatedPropertyType logic.

- SVGElement::animatedPropertyTypeForAttribute() was deprecated. |SVGElement::animatedPropertyTypeForCSSAttribute()| is provided to retrieve CSS types.
- |SVGAnimateElement::determineAnimatedPropertyType()| is moved to SVGAnimationElement, and its argument is omitted.
-- Its argument was always targetElement()
-- This removes the need for cast in |SVGAnimationElement::currentValuesForValuesAnimation()|

BUG=349370

Review URL: https://codereview.chromium.org/180113007

git-svn-id: svn://svn.chromium.org/blink/trunk@168615 bbb929c8-8fbe-4397-9dbb-9b2b20218538