Minor API pain-points

These are things that are easy to workaround downstream, but would one-liner if we had upstream support. I will update the list as I find more things:
1) Direct API for calculating assetid and token id directly from prevouts during initial issuance. This currently a multi step process which requires dealing calling the AssetId::generate_asset_entropy() API.
2) Display implementations of Explicit Asset should add the 0x01 prefix
3) Add FromStr implementation for confidential::Asset/Value/Nonce. Currently, we need to decode a bytes and call `encode::deserialize`. It would be great to have methods for a) from_slice/to_vec() b) Display/FromStr c) FromHex/ToHex.
4) Implement auto-derives for Error data structures. For example: `UnBlindError`.
5) Separate out TxOut::unblind API into two APIs. TxOut::unblind_from_prf. This will also it to re-use it for psbt logic too

Start by reading the listed AssetId::generate_asset_entropy(), Explicit Asset Display, confidential::Asset/Value/Nonce, UnBlindError, and TxOut::unblind entry points. The issue groups five separate API requests, so first separate and scope them against the existing Rust transaction and PSBT code. Done would require an agreed scope and corresponding implementations for the selected requests, with behavior covered by the project’s existing checks.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.