Add PSBT and wallet RPC methods (#32)

* Add PSBT and wallet RPC methods

Implements wallet_create_funded_psbt, wallet_process_psbt, finalize_psbt,
psbt_bump_fee, get_address_info, and list_unspent_with_options.

Key improvements:
- Comprehensive docstrings following codebase conventions
- Type-safe CreateRawTransactionOutput enum instead of HashMap
- Transaction hex deserialization in WalletProcessPsbtResult
- BIP 174 test vector for realistic PSBT testing
- Removed incorrect locktime field from wallet responses
- Added psbtbumpfee support for Payjoin compatibility

* meta: bunch fixes

* fix: we don't have walletfinalizepsbt

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Co-authored-by: Jose Storopoli <[email protected]>

Author: bc1cindy