Expand the transaction generator to sometimes merge UTXOs

[Geod24]

Currently, Faucet will forever split the outputs among keys.
This is a very predictable behavior that does not reflect a live settings.

We currently only have the following variables:

• Interval: how often we send
• Count: How many transactions we generate per run

What we don't have is a way to control the structure of the transactions. We don't need to send homogenous transactions, and we definitely need to send transactions what will "merge" UTXOs (have inputs.length > outputs.length) as opposed to the current approach of always "splitting" (inputs.length < outputs.length).