Extensions Speedup

Speedup extensions coping near root node.

File	1.2.2 (APPIMG)	master (APPIMG)	pr (APPIMG)	master	pr
TEST A	3m31.523s	1m46.798s	33.785s	1m23.582s	36.200s
TEST B	15.976s	15.585s	15.250s	9.940s	9.870s
TEST C	11.782s	12.294s	11.531s	5.839s	5.764s

TEST A

https://gitlab.com/inkscape/inbox/uploads/6db7c183dd03f3620ad93877cbd1e750/National_Grid_drawing.svgz
time ./inkscape --batch-process --actions="org.inkscape.qr-code.noprefs" National_Grid_drawing.svgz -o outfile.svg

TEST B

https://gitlab.com/inkscape/inbox/uploads/d4cd015225b2d82e6488035f193ef7f3/madrid.svg
time ./inkscape --batch-process --actions="org.inkscape.qr-code.noprefs" madrid.svg -o outfile.svg

TEST C

https://gitlab.com/inkscape/inkscape/uploads/22535b3443e1faef9335cab807a3d37a/circle.svg
time ./inkscape --batch-process --actions="org.inkscape.qr-code.noprefs" circle.svg -o outfile.svg

Thanks @pbs3141 and @speleo3 for share this files and process