Fix displayed units for BMW Connected Drive

[rikroe]

Proposed change

Fixes the displayed sensor units (_attr_native_unit_of_measurement) depending on the HA unit system, which was broken due to #75225 (value conversion worked, but unit was wrong for imperial).

Type of change

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

Additional information

• This PR fixes or closes issue: fixes Numbers are in imperial units but until labels are metric #76542, fixes 20220716.1 Forces metric units? bimmerconnected/ha_custom_component#52
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
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• Tests have been added to verify that the new code works.

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[probot-home-assistant]

Hey there @gerard33, mind taking a look at this pull request as it has been labeled with an integration (bmw_connected_drive) you are listed as a code owner for? Thanks!
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[davet2001]

Could you add a test to verify the new behaviour especially showing metric/imperial units now working correctly?

[rikroe]

Adding "a test" was more effort as I had to setup a test base. However thanks for the hint, being able to test in HA surely makes sense!

[rikroe]

Just refactored the test to use a pytest fixture and streamlined it to use the same vehicle as #74871.
If this gets merged before, I'll update the other PR accordingly.

Unfortunately this was quite a lot of code change in the tests again, but I hope I included everything you need and it will be much easier to write tests in the future.

[MartinHjelmare]

Looks good!