Adds GrpcDiscoveryClient for enumerating gRPC services via server reflection.
Includes:
- GrpcDiscoveryClient class with listServices(), discoverAllServices() methods
- Support for getting file descriptors for symbols and filenames
- DiscoveredService and DiscoveredMethod data classes
- Custom exceptions (ReflectionException, ConnectionException)
- Generated proto files for gRPC reflection (fixed for protobuf 6.0.0)
Co-Authored-By: Claude <noreply@anthropic.com>
