**Description**

Currently `BaseOperator` and `XComArgs` implements the same logic of `__lshift__`, `__rshift__` and others "chain" operations (`>>`, `<<`). It seems resonable to abstract this logic into `TaskMixin` to introduce some DRYness especially because the new concept of `TaskGroup` will also implement the same methods.

**Use case / motivation**

Limit duplication of logic.

**Related Issues**

https://github.com/apache/airflow/pull/10827#issuecomment-691927501
#10153 

airflow/models/baseoperator.py
"""
        This hook is triggered right after self.execute() is called.
        It is passed the execution context and any results returned by the
        operator.
        """
    def on_kill(self) -> None:
        """
        Override this method to cleanup subprocesses when a task instance
        gets killed. Any use of the threading, subprocess or multiprocessing
        module within an operator needs to be cleaned up or it will leave
        ghost processes behind.
        """
    def __deepcopy__(self, memo):
        """
        Hack sorting double chained task lists by task_id to avoid hitting
        max_depth on deepcopy operations.
        """
        sys.setrecursionlimit(5000)  
        cls = self.__class__
        result = cls.__new__(cls)
        memo[id(self)] = result
        shallow_copy = cls.shallow_copy_attrs + \
            cls._base_operator_shallow_copy_attrs  
        for k, v in self.__dict__.items():
            if k not in shallow_copy:
                setattr(result, k, copy.deepcopy(v, memo))  
            else:
                setattr(result, k, copy.copy(v))
        return result
    def __getstate__(self):