fix(data): Allocate empty array on tw_data_create_with_bytes if data is NULL

[satoshiotomakan]

This pull request refactors memory handling in the Rust FFI layer to simplify error handling and improve API consistency. The main change is that methods like CByteArrayRef::to_vec() and CByteArrayRef::as_slice() now always return a value (empty if pointer is NULL), instead of an Option. Additionally, a new test is added for Ethereum Barz authorization with an empty-array representation of zero nonce.

Memory API refactoring

• rust/tw_memory/src/ffi/c_byte_array_ref.rs: Changed CByteArrayRef::to_vec() and CByteArrayRef::as_slice() to always return a value (empty on invalid input), removing Option from their signatures. [1] [2]
• rust/tw_memory/src/ffi/tw_data.rs: Updated TWData::from_raw_data() to always return a TWData and refactored tw_data_create_with_bytes() to remove error handling for null pointers. [1] [2]
• rust/tw_memory/src/ffi/tw_string.rs: Simplified TWString::is_utf8_string() to remove error handling for invalid input.

FFI function simplification

• rust/tw_keypair/src/ffi/privkey.rs, rust/tw_keypair/src/ffi/pubkey.rs, rust/tw_keypair/src/ffi/asn.rs: Removed error-handling macros (try_or_else!, try_or_false!) from FFI functions, relying on the new memory API to return empty values on invalid input instead. [1] [2] [3] [4] [5] [6]

Testing improvements

• tests/chains/Ethereum/BarzTests.cpp: Added a new test case for signing Ethereum Barz authorization with a zero nonce to verify correct handling of empty nonce input.

[github-actions]

Binary size comparison

➡️ aarch64-apple-ios: 14.11 MB

➡️ aarch64-apple-ios-sim:

- 14.11 MB
+ 14.11 MB 	 -1 KB

➡️ aarch64-linux-android:

- 18.57 MB
+ 18.57 MB 	 -1 KB

➡️ armv7-linux-androideabi: 15.53 MB

➡️ wasm32-unknown-emscripten:

- 13.23 MB
+ 13.23 MB 	 -1 KB