Implement exception handling and try-catch-finally support

Adds support for WebAssembly exception handling, including throw, try, catch, and finally constructs. The compiler now emits proper throw instructions and manages exception tags when the exception-handling feature is enabled. Try-finally and try-catch-finally blocks are compiled with correct control flow, including deferred returns and pending action dispatch. Flow context is extended to track try-finally state. Adds comprehensive tests for exception handling.

Author: BlobMaster41