feat(types): Add comprehensive gmpy2 type stubs

Add detailed type stubs for gmpy2 library to improve type checking and IDE support in the Post-Quantum Feldman's VSS implementation. Includes:
- Complete type definitions for mpz, mpq, mpfr, and mpc classes
- Type hints for arithmetic operations and comparisons
- Exception class definitions
- Utility function signatures
- Proper handling of generic types and unions

Author: DavidOsipov