SVG elements (except the outermost <svg>) use SVG's coordinate system,
not the CSS box model, so CSS positioning doesn't apply to them.
This adds SVGElement::adjust_computed_style() to force position:static
on all SVG elements except the outermost <svg> element (which has no
owner_svg_element()). SVGSymbolElement's existing override now calls
Base::adjust_computed_style() to inherit this behavior.
With this in place, the FIXME in layout_absolutely_positioned_element()
for SVG boxes becomes unreachable and is replaced with
VERIFY_NOT_REACHED().
Inline nodes in our layout tree have a position, so let's show it. By
centralizing the logic for this, block nodes now lose their redundant
'content-size' dump info which is already part of the box model dump.
