Allow "infinite vector" zoom in the form editor

Allow "infinite vector" zoom in the form editor.

Currently, we render all items at the original resolution and zoom in on the pixels.
We could offer a mode in which we increase the resolution while zooming in.

For document-level SVG and text items, this would be easy. But typically the document contains
sub-components that would have to be rendered at a higher resolution because we do not know how they work internally.
Rendering items at higher resolution might take a lot of memory.

We could implement this in a naive way up to a zoom level of 4x which might be sufficient for most use cases.

Zooming in would not be wysiwyg anymore.