* Start moving parts of yaml utils to own module
Move parts of yaml loader out of the single large file and start
to create the structure of the yaml loaders in Ansible [0].
[0]: https://github.com/ansible/ansible/tree/devel/lib/ansible/parsing/yaml
* Finish yaml migration, update tests and mocks
* Move code around to finish the migration
* Update the mocks so that `open` is patched in
`homeassistant.util.yaml.loader` instead of
`homeassistant.util.yaml`.
* Updated mypy ignores
* Updated external API of `homeasistant.util.yaml`, see below:
Checked what part of the api of `homeassistant.util.yaml` was actually
called from outside the tests and added an `__ALL__` that contains only
these elements.
Updated the tests so that references to internal parts of the API (e.g.
the yaml module imported into `homeassistant.util.yaml.loader`) are
referenced directly from `homeassistant.util.yaml.loader`.
In `tests/test_yaml.py` the import `yaml` refers to
`homeassistant.util.yaml` and `yaml_loader` refers to `~.loader`.
Future work that remains for the next iteration is to create a custom
SafeConstructor and refers to that instead of monkey patching `yaml` with
custom loaders.
* Update mocks in yaml dumper, check_config
## Description:
More typing improvements.
Switch to using `mypy.ini` for flexibility
Add `warn_return_any` check except in `homeassistant.util.yaml` that does typing hacks. Fix some type annotations as resulting from this check and ignore others were fixing is hard.
## Checklist:
- [x] The code change is tested and works locally.
- [x] Local tests pass with `tox`. **Your PR cannot be merged unless tests pass**
