Replace the onion-glyph with dedicated icon for onion services

As part of our wider push to reduce the use of the onion-glyph (i.e. the flattened version of Tor Browser’s application icon) for application-agnostic features, @nicob has created a new icon to represent onion services:

Here are the SVGs:

• onion-site.svg
• onion-site-warning.svg
• onion-site-broken.svg

Here are some mockups:

.onion available

Normal

Warning

Broken

Android

And the Figma file's ready for dev-handoff here: Figma link

N.B. Please refer back to the standard security (i.e. padlock) icon when selecting theme-based color fills. I've got no idea if the red we've used is correct, or if it's theme-specific.