Velbus: Use EntityDescription for sensors, Finish typing

[cereal2nd]

Proposed change

• Finish typing the whole module
• Switch the sensor platform to work with EnityDescriptions

Note: this is dependant on #58622

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)
• 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 #
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• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
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[probot-home-assistant]

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

Please split the PR into two PRs. One for completing typing and one for adding entity descriptions.