Feature: add scene history sensor

[samuelncui]

MihomeSceneHistorySensor can create virtual switches easily. This new sensor allows users to use Xiaomi AI Speakers to control home assistant devices.

By adding automation as follows:

alias: Do something when command to Xiaomi AI Speaker
description: "xxxx"
trigger:
  - platform: state
    entity_id:
      - sensor.mi_xxxxxxxxx_xxxxxxxxx_scene_history
    attribute: scene_id
    to: "123454654" // scene id
condition: []
action:
  - some action
mode: single

Refactor async_get_devices and async_get_homerooms for easier understanding.

[samuelncui]

已经测试很久了，可以帮忙合并一下吗？怕后面修改又不兼容了。