ha-area-picker: change "sorting_label"

[ildar170975]

Breaking change

Proposed change

Currently in ha-area-picker areas are sorted by their names.
Since
--areas may belong to floors,
--since we can set a "level" option for each floor aimed to define a physical position of a floor,
this PR proposes a different sorting order based on that "level" value (where applicable).

In the example below, we have 4 floors (cellar -> basement -> 1st floor -> 2 floor) with levels "-1, 0, 1, 2" (levels are manually assigned to floors by users).
Now these areas sorted from the "cellar" to "areas not assoc. to floors":

Warning:
This approach MAY conflict with #27986.
But in that #27986 - imho - the "level" property is not used, although I believed that exactly that "level" property should be used by users to define a physical location.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io