chore: log panics inside udf

[yhl25]

2024/08/29 09:24:07 panic inside reduce handler: reducer should not be invoked goroutine 26 [running]:
runtime/debug.Stack()
	/usr/local/go/src/runtime/debug/stack.go:24 +0x64
github.com/numaproj/numaflow-go/pkg/reducer.(*reduceTaskManager).CreateTask.func1.1()
	/Users/yhl01/Documents/numaproj/numaflow-go/pkg/reducer/task_manager.go:94 +0x40
panic({0x3f73c0?, 0x556758?})
	/usr/local/go/src/runtime/panic.go:770 +0x124
main.reduceCounter({0x400017e040?, 0x9?}, {0x9?, 0x9?, 0x0?}, 0x0?, {0x40000465e8?, 0x32e2e8?})
	/Users/yhl01/Documents/numaproj/numaflow-go/pkg/reducer/examples/counter/main.go:12 +0x2c
github.com/numaproj/numaflow-go/pkg/reducer.reducerFn.Reduce(0x4000046598?, {0x55bbf0?, 0x4000168d50?}, {0x40000970d0?, 0x0?, 0x4000169f80?}, 0x10?, {0x5583c0?, 0x4000097410?})
	/Users/yhl01/Documents/numaproj/numaflow-go/pkg/reducer/interface.go:62 +0x58
github.com/numaproj/numaflow-go/pkg/reducer.(*reduceTaskManager).CreateTask.func1()
	/Users/yhl01/Documents/numaproj/numaflow-go/pkg/reducer/task_manager.go:101 +0xfc
created by github.com/numaproj/numaflow-go/pkg/reducer.(*reduceTaskManager).CreateTask in goroutine 24
	/Users/yhl01/Documents/numaproj/numaflow-go/pkg/reducer/task_manager.go:90 +0x33c
2024/08/29 09:24:07 received shutdown signal
2024/08/29 09:24:07 gracefully stopping grpc server
2024/08/29 09:24:37 forcefully stopping grpc server
2024/08/29 09:24:37 grpc server stopped