[SVG] Remove old SVGAnimatedProperty implementation.

This CL removes old SVG animated property implementation, SVGAnimatedProperty.
SVGElementAnimatedPropertyList is also removed, as the property list only contained old SVGAnimatedProperty instances and thus was always empty. |Vector<SVGElement*> m_animatedElements| is now managed instead.




BUG=349370

Review URL: https://codereview.chromium.org/192483002

git-svn-id: svn://svn.chromium.org/blink/trunk@168815 bbb929c8-8fbe-4397-9dbb-9b2b20218538