Bugfix group order

[balloob]

Description:
As part of my PR #3203 to add reloading config to groups I introduced a bug when cleaning up the voluptuous schema validation that broke the group ordering based on their order in the config.

The problem is that passing an ordered dict through a voluptuous dictionary validator will convert it to a normal dictionary. The group component depends on the order from the config to calculate the order of groups so this caused an issue.

This PR adds a new config validator to validate ordered dictionaries while maintaining the order.

I think that we should release this as part of 0.28.1

Example entry for configuration.yaml (if applicable):

group:
  kitchen:
    name: Kitchen
    entities:
      - switch.kitchen_pin_3
  upstairs:
    name: Kids
    icon: mdi:account-multiple
    view: yes
    entities:
      - input_boolean.notify_home
      - camera.demo_camera
      - device_tracker.demo_paulus
      - group.garden

Checklist:

If the code does not interact with devices:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• Tests have been added to verify that the new code works.

[MartinHjelmare]

Should report that [val] is invalid, right?

[balloob]

No, as it is the path to the value. So actually the 'key' one is not completely correct I guess. But with the patch from @kellerza that doesn't matter anymore so I'll stick with his work.

[MartinHjelmare]

One comment. Changes look good to me, but I'm not too familiar with the old behavior of groups.

[kellerza]

Proposal for changes here

Validating as full entries raises the correct error

voluptuous.error.MultipleInvalid: extra keys not allowed @ data['group']['travel_johann']['xname']

otherwise it does not include the group name:

voluptuous.error.MultipleInvalid: extra keys not allowed @ data['group']['xname']

[balloob]

Thanks @kellerza, I've merged your changes. I've actually simplified it a bit more. From further inspection of the voluptuous code it seems like they will only report one error at a time . So I decided to do that too.

[kellerza]

Short and simple! Looks like I introduced a linting error though...