Serialize padding state machine in consensus

We should have the ability to list padding machines in the consensus.

This might not make 041.

Trac:
Child Ticket(s): #28638 (moved)

added component::core tor/dirauth points::15 priority::low severity::normal sponsor::2 status::new type::defect wtf-pad labels

Trac:
Points: 8 to 15

Take some wtf-pad stuff out of 041-proposed

Trac:
Keywords: 041-proposed deleted, N/A added

Lowering priority: while I think there will be lots of research interest in different types of padding machines, I don't think the actual machine updates will require update via consensus until we start producing many different types of machines for different quantities of spare consensus overhead, which is a long way off.

I think #29203 (moved) plus #29098 (moved) plus the existing global consensus padding rate limits are way more immediately useful for reacting to different amounts of network load than swapping machines in and out entirely on the fly, at least until we learn more.

Trac:
Priority: Medium to Low

changed time estimate to 120h

moved to tpo/core/dirauth#29102