When a text node changes inside an absolutely positioned element within
an SVG <foreignObject>, and the abspos element's containing block is
outside the SVG subtree, the layout invalidation was incorrectly
stopping at the SVG root boundary. This triggered partial SVG relayout,
which cannot re-layout the abspos element since it's laid out by its
containing block's formatting context (outside the SVG).
The previous check only tested whether `this` (the node triggering
invalidation, e.g. a text node) was absolutely positioned, missing the
case where an abspos *ancestor* in the path has its containing block
outside the SVG. Fix this by walking from `this` up to the SVG root and
checking every abspos node in the path. If any has a containing block
outside the SVG subtree, skip the SVG boundary so layout propagation
continues upward and a full layout runs.
