Fix xiaomi_ble not remembering a device is a sleepy device

[bdraco]

Proposed change

We did not store if the device was sleepy which meant as soon as HA was restarted, the integration would forget that the device was sleepy.

This is not very useful yet, but will be once #97462 is done

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
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• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
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Additional information

• This PR fixes or closes issue: fixes #
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[home-assistant]

Hey there @Jc2k, @Ernst79, mind taking a look at this pull request as it has been labeled with an integration (xiaomi_ble) you are listed as a code owner for? Thanks!

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[bdraco]

Thanks