Add type constraints for variadic functions in test generator #1182

Currently, the generateFunctionExpression method doesn't properly handle the type constraints for variadic functions. When generating random expressions for testing, it doesn't consider the allowed parameter types for variadic functions, potentially creating invalid test cases.

Proposed change
Implement the TODO comment by:
Add support for type-specific argument generation in variadic functions by implementing the existing TODO comment.

1. Adding a mechanism to specify allowed parameter types for variadic functions
2. Using those constraints when generating random expressions for testing
3. Ensuring the generated function calls respect the function signature