Small fixes for Orchard/ZSA backward compatability in Librustzcash

[alexeykoren]

No description provided.

[what-the-diff]

PR Summary

• Enhanced Error Handling
  The BuildError enum in the builder.rs file has been expanded to include two new variants (BurnErrorNative and BurnErrorZero), providing a more comprehensive and specific breakdown of possible errors. This is further supported by the implementation of the Display trait, augmenting readability and understandability of the error message.

• Improved Function Updates
  The add_burn function, part of the Builder struct in the builder.rs, now has an improved return type. It provides a Result with the expanded BuildError as the error type, replacing the previously used &'static str. Additionally, a new method map_proof has been incorporated into InProgress struct, also found in builder.rs.

• Module Renaming and Addition
  The domain module in note_encryption.rs has been renamed to pub mod domain for better visibility and naming consistency. Additionally, a new file domain.rs has been added to the note_encryption directory.

• Enhanced Struct and Function
  A new method from_data has been added to the Signed struct residing in issuance.rs. Furthermore, the build_and_verify_bundle function in zsa.rs has been updated to handle the new returns from the add_burn function.

[PaulLaux]

very nice
@dmidem should merge when ready