Change remixed/Friends remixed

[Kruwed]

The "Fresh Bitcoin" stat was changed awhile back to exclude one hop coinjoin outputs that were remixed and do not pay coordinator fees. This includes the sender's change output as well as coins sent from one Wasabi user to another. We should still track the value of these coins that mix for free.

Furthermore, there is a noticeable on chain footprint that can be used determine when the "friends don't pay" discount is taken advantage of: Whenever a payment consuming coinjoin outputs creates two outputs, and BOTH outputs are remixed, then we can assume two Wasabi users are transacting. This is an upper bound- if the change avoidance feature is used by the sender, then the use of this discount by the receiver will not be detected.

[Kruwed]

All 4 discounts can be visualized on one chart, this metric only applies to Wasabi 2.0:

"Free Change" - 2 output transaction where one output (the change) was remixed for free.
"Free Consolidation" - 1 output transaction that was remixed for free. This could be a payment between two Wasabi users, or a UTXO consolidation from a Wasabi user spending coins to himself.
"Friends Don't Pay" - 2 output transaction where both outputs remix for free. This is definitely a payment between two Wasabi users.
"Plebs Don't Pay" - Total value of new inputs below 0.01 that were not charged coordinator fees.

An issue is that a coin can qualify for both the "Plebs don't pay" exemption in addition to a "Friends don't Pay" or "Free Change" exemptions. I do not know whether it is best to double count this or to prioritize one discount over the other.