Currently the size of our distribute package is up to
800MB, this patch is migrate python gateway server into
api server
The distribute package size before and after this patch is:
```sh
# before
796M apache-dolphinscheduler-2.0.4-SNAPSHOT-bin.tar.gz
# after
647M apache-dolphinscheduler-2.0.4-SNAPSHOT-bin.tar.gz
```
* [python] Fix change exists pd attribute user error
* Remove attribute from class ProcessDefinition, cause it should to
object User instead of object ProcessDefinition.
* Grant project to user if attribute user change for exists ProcessDefinition
close: #8751
* Add py.test conftest.py for package integration
* Change `yaml_parser.py` method `to_string` to magic method
`__str__` make it more pythonic.
* Add some tests to magic method `__str__` and `__repr__`
* [python] refactor yaml file parser
* Change yaml parser package to ruamel.yaml
* Refactor configuration.py module
* And file.py to write file locally
* Add more tests on it
close: #8593
* Fix UT error
* Remove pypyaml from tests
* Fix file error when param create is False
* Fix error logic
* And tests to avoid regression
Jiajie Zhong