[v4] [icons] fix: icon paths are right-side up

[adidahiya]

Checklist

• Includes tests
• Update documentation

Changes proposed in this pull request:

• Revert to the old method of generating the icon path strings using the svgo package
  • Before this change, we were parsing the output SVG font output of fantasticon, which for some reason was rendering all paths upside-down.
  • Now, we no longer need the CSS transform to flip the svg in the icon component, and consumers who reference IconSvgPaths16 / IconSvgPaths20 don't have to add that unnecessary transform either
• The type of IconSvgPaths16 / IconSvgPaths20 has been reverted to its type in v3.x, so we no longer have that API break as part of the 4.0 changes

Reviewers should focus on:

Icons page renders correctly

Screenshot

[blueprint-bot]

remove extraneous code comment

Previews: documentation | landing | table | modern colors demo