Estimate user-facing transaction volume and count

[elsirion]

Some transaction patterns, such as making a lightning payment, involve multiple Fedimint transactions. Currently, these are all counted in the volume and transaction count statistics. It would be nice to develop heuristics to estimate the actual volumes/transaction counts that a user would experience.

Things to take into account:

• LN transactions involve multiple FM transactions (fund contract, redeem contract and post offer in case of incoming)
• Ecash transactions sometime necessitate creating the exact denominations beforehand, causing an additional transaction. We could simulate user behavior to estimate how often that happens to then adjust the ecash volume
• All transactions have the potential to generate change if no exact ecash could be found

[tacio]

Getting to 100% accuracy for user-facing transaction volume is impossible, and the effort grows fast. So I suggest we do one thing at a time

1. LN and LNv2 deduplication
2. Rebalance volume estimation
3. Transactions from federation service providers (gateway liquidity, stability pool provider); currently impossible with only FMO data, but has a big impact on transaction volume.

There is also the issue that we won't have the decoder for custom modules, but we can always look at the mint side of a transaction to get the amount.