fix appendix icon numbering/order

[gavin-ts]

Summary

Fixes incorrect appendix icon numbering.

Details

• fixes Tooltip numbering wrong in PNG export #1703
• appendix tooltip/link icons used to be replaced in the svg according to their numbered order, but the icons in the svg are ordered according to the render order
• fixes appendix creation to replace each rendered icon with the correct number icon

example from #1703

X is defined first so X should get 1 and Y 2, but X is rendered after Y and all the other 1st level shapes because it has to appear in front of its parent container.
Previously this meant the 1st icon in the svg was Y's icon which was incorrectly replaced with a 1 icon.

Block: {
  X: {tooltip: X}
}
Y: {tooltip: Y}

before

after