Switch HeroIcons to ReactIcons

[melanke]

HeroIcons has a very small subset of icons, while ReactIcons includes HeroIcons and many other icon packs, allowing a greater variety of options. Since we only ship what we are importing, I don't see a good reason not to use a bigger icon library.
As a mentor of the BG Batches, I often see developers importing other icon libraries or adding SVG icons to the project, so I believe this would make the developer experience much more enjoyable.