Fix bug in derivative sensor when source sensor's state is constant

[jgrande]

Proposed change

Previously, when the source sensor's state remains constant, the derivative sensor repeats its latest value indefinitely instead of reporting zero. See: #83496

This patch fixes this bug by consuming the state_reported event and updating the sensor's output even when the source sensor doesn't change its state. Once the derivative sensor reaches zero, it will ignore any further state_reported events.

The change was tested by running pytest tests/components/derivative and running it in my own HA instance for about a week.

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 Derivative integration gives incorrect values when source does not change #83496

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• I have followed the perfect PR recommendations
• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.

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• I have reviewed two other open pull requests in this repository.

[home-assistant]

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[home-assistant]

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[home-assistant]

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

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Stale

[elupus]

Nice! Thanks!

[EDelsman]

Thanks!