New address encoding

[louisinger]

This PR adds the new ark address encoding, replacing bare user public key by vtxo taproot key. It implies change on the APIs and the SDK.

Address encoding

An ark address is network prefix + VTXO taproot pubkey + ASP pubkey encoded with bech32m.

ark1x0lm8hhr2wc6n6lyemtyh9rz8rg2ftpkfun46aca56kjg3ws0tsztfpuanaquxc6faedvjk3tax0575y6perapg3e95654pk8r4fjecs5fyd2

• network prefix identifies testnet, mainnet, regtest...
• VTXO taproot pubkey is the P2TR key that should be used as scriptpubkey in VTXO leaf output of the tree.
• ASP pubkey allows verifying the ASP of the address

API & server changes

• remove descriptor from RegisterOutputsForNextRound RPC, only ark address is expected.
• expect descriptor to be revealed while spending VTXO = RegisterInputsForNextRound RPC.
• [db] VTXO table: drop descriptor field, replace by pubkey field.

@altafan @tiero please review

[altafan]

[db] VTXO table: drop descriptor field, replace by address field.

@louisinger let's replace the descriptor with the taproot pubkey instead of the address:

• we don't want to "depend" on network as address contains a network prefix
• we don't want to persist the same server pubkey for all records