A collection of TxBuilder issues

[danielabrozzoni]

My hackmd proposal for the txbuilder redesign: https://hackmd.io/YJFF7q_lTDiYoQGzgT8ogw

All the txbuilder-related github issues:

• Redesign TxBuilder #899
• CS fallback algorithm can't be changed (we probably never created an issue for this? But the idea is that we once had the bnb algorithm with the single random draw fallback, and the fallback wasn't customizable)
• (Somewhat related) Remove Database type paramter from CoinSelectionAlgorithm #281
• Let TxBuilder avoid previously used UTXOs (UTXO locking) #849
• Substitute enable_rbf in TxBuilder with disable_rbf #791
• Support merging multiple transactions while bumping the fees (https://github.com/bitcoindevkit/bdk/blob/master/crates/bdk/src/wallet/mod.rs#L1017)
• TxBuilder::add_psbt #153
• Coin selection should include checks to avoid creating ambiguous transaction history. #706
• Expose way to select only (n-)confirmed UTXOs for TX creation #1029

[notmandatory]

@danielabrozzoni and @evanlinjin could some of these issues be done as non-api-breaking new features to TxBuilder? If so I'd like to see if we can target those for a 1.1 release. In particular #153, #706, #849 and #1029 look like good candidates.