feat: Migrate SAL to Cargo workspace

- Migrate individual modules to independent crates
- Refactor dependencies for improved modularity
- Update build system and testing infrastructure
- Update documentation to reflect new structure

vault/README.md

@@ -141,6 +141,8 @@ cargo test crypto_tests
 cargo test rhai_integration_tests
 ```
 
+**Note**: The Rhai integration tests use global state and are automatically serialized using a test mutex to prevent interference between parallel test runs.
+
 ## Dependencies
 
 - `chacha20poly1305`: Symmetric encryption