Add suggested precision for Airthings BLE integration

[LaStrada]

Breaking change

Proposed change

Sometimes, certain sensors on Airthings devices return values with many decimal places. This PR introduces a suggested_display_precision attribute for most entities, either 1 or 2 decimal. Some entities have text-based (e.g. radon short/long term averages).

This update is necessary to prepare for the inclusion of newer devices, which may provide values with even more decimal places. Support for these devices will be added in a separate PR.

From a Wave Mini:

From a Wave Enhance (not supported yet). As shown, the pressure entity can display a significant number of decimal places:

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 #
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[home-assistant]

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

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