Add settings domain and repo

[altafan]

Atm we have only some of the config env vars persisted in storage and that can update at runtime via admin apis.

Let's add a new Settings domain and related repo interface with usual CRUD apis so that we can change at will:

• ban threshold and duration
• delays
• batch max/min participants
• vtxo/utxo min/max amount
• settlement min expiry gap
• vtxo cutoff data to skip csv validation
• max tx weight

The domain can also house the existing domains for fee and scheduled session config (maybe better to keep distinct tables tho?)

All the relative env vars can be dropped alongside with these changes

[bitcoin-coder-bob]

working off PR: #939