Created by: JepsonWong
add ci check for dygraph optest. check_dygraph字段表明是否跑相应op的动态图单测。不允许开发者直接设置check_dygraph字段，该字段默认设置为True，会执行相应op的动态图单测。如果需要改动check_dygraph字段，需要对应审核人review。(The check_dygraph field indicates whether to run the dygraph optest. The developer is not allowed to set the check_dygraph field. By default, this field is set to True, and the dygraph optest will be executed.)
新增的CI检查规则只检查一个PR中新增代码中是否包含check_dygraph的设置。
CI检查点：
- 开发者设置了check_dygraph字段，类似"check_dygraph="的写法。
CI检查失败提示： 0. Developers are not allowed to set the check_dygraph field directly, which is set to True by default. If you need to change the check_dygraph field, you must have one RD (phlrain (Recommend) or lanxianghit) review and approve. The code that do not meet the specification are as follows:
- python/paddle/fluid/tests/unittests/test_squeeze_op.py :
- self.check_output(check_dygraph=False)
- self.check_grad(["X"], "Out", check_dygraph=False)
- python/paddle/fluid/tests/unittests/test_unsqueeze_op.py :
- self.check_output(check_dygraph=False)
