Add Optional Negate Field to Grid/Battery Power Schema

[TCWORLD]

Proposed change

This adds optional preference entries needed for configuring whether the Grid and Battery power sensors for the energy dashboard have inverted polarity.

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

• Link to frontend pull request: Add Polarity Invert option to Power sensors in Energy dashboard frontend#28397

Checklist

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[home-assistant]

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