Fix some issues with QNN

[Zhaoyilunnn]

1. When using real machine, backend is not configurable due to mistakenly override config:

   pyquafu/quafu/algorithms/estimator.py

   Lines 56 to 57 in 2c5f0bb

   	self._task.config(backend=self._backend)
   	self._task.config(**task_options)

2. The old submit interface now should send job synchronously:

   pyquafu/quafu/tasks/tasks.py

   Line 168 in 2c5f0bb

   res = self.send(qc)

3. Make send configurable based on env config files (WIP)