Sauteed Onion for all TPO Onion Service sites

Evaluate and eventually implement Sauteed Onions in all TPO Onion Service sites. Tasks involved:

• Evaluate/propose adoption in all TPO sites. Initial estimate from #66 (closed) is that this could be done quickly and without much effort.
• Check TPA's availability and check if they could review the discussion.
• Move this ticket to TPA when the time comes.