feat: detect multiple UTXOs per output

[michael1011]

This PR refactors the way UTXOs and addresses are handled by separating the UTXOs and outputs (scripts of the addresses) in the database which means that:

• every address can have multiple UTXOs in an efficient way (also known as address reuse; should be avoided if possible)
• there are no problems if a single transaction sends funds to multiple addresses of Boltz (the transaction hash used to be the primary key of the utxos table in the database)
• Boltz listens new transactions on all addresses the wallet ever created. Before this PR Boltz forgot about old addresses it created on every restart.

This is a breaking change to the database. Please remove your existing boltz.db before running Boltz.