Fix ungrouping: linked grand-children, grand-child source

Transform of linked items (linked offset, text-on-path, text with shape-inside) must only be compensated if their source is a direct child of the group being ungrouped. This also applies to linked items which are not direct children of the group.

Test case: complex-group.svg

Ungroup the top-level group. All items should stay in place (slight font-skewing is expected, but font-size must be preserved).