Don't use get_resource_path from traits

See comment: https://github.com/enthought/traits/issues/1424#issuecomment-766857595

> * get_resource_path
This uses evil magic and its use should be avoided if at all possible. Pyface should find a better way of doing whatever it's doing. It's not used within Traits anywhere, and it's not tested anywhere."

Uses are:
https://github.com/enthought/pyface/blob/2974f580c4c10ec4142641ca67b15ec27593c5ae/pyface/ui_traits.py#L29
https://github.com/enthought/pyface/blob/2974f580c4c10ec4142641ca67b15ec27593c5ae/pyface/image/image.py#L62
https://github.com/enthought/pyface/blob/2974f580c4c10ec4142641ca67b15ec27593c5ae/pyface/resource/resource_path.py#L19