feat(wasm-utxo): add fixed script wallet outputs implementation

This PR implements the BitGo Fixed Script wallet outputs functionality,
which allows generating BitGo 2-of-3 wallet output scripts for various
script types including P2SH, P2WSH, and Taproot.

The code includes:
- Core wallet script generation code
- Modular organization by script type
- Support for traditional and MuSig2 key path spending
- Comprehensive test fixtures and validation
- Utilities for handling public key derivation

Issue: BTC-2652

Co-authored-by: llm-git <[email protected]>

Author: OttoAllmendinger

packages/wasm-utxo/src/fixed_script_wallet/mod.rs

@@ -1 +1,11 @@
+/// This module contains code for the BitGo Fixed Script Wallets.
+/// These are not based on descriptors.
+mod wallet_keys;
+
 pub mod wallet_scripts;
+
+#[cfg(test)]
+pub mod test_utils;
+
+pub use wallet_keys::*;
+pub use wallet_scripts::*;