vector: Add SVG versions of collapsible menu icons

SVG with a PNG fallback is added for the collapsible tab icon.
It allows SVG-capable browsers to view images at full resolution
while keeping backwards compatibility with browsers that don't support
SVG.

Implementation similar to I914da06494.

Change-Id: I0448e34bd10aa5cf83f1530a44b1555caee271b1
Merge "vector: Add SVG versions of collapsible menu icons"