Is your feature request related to a problem? Please describe.

The trashcan and zoom control assets don't scale well and aren't convenient to style.

Describe the solution you'd like

Use svg assets for the trashcan and zoom controls while still supporting png, if it is provided (backwards compat).

Describe alternatives you've considered

Additional context
App Inventor colors the trashcan and zoom controls back due to some accessibility concerns. I think they have to monkey patch in order to do this, so changing this in core would be helpful.