Update statistics chart to respect entity display precision, fix precision bug in history chart

[karwosts]

Proposed change

Allow statistics chart graph tooltip to get a display precision from an entity's settings. Previously seems hardcoded to two decimal places.

Also fixes a bug in history-graph use of display precision where the wrong dataset index is used when an entity has multiple datasets (like a climate entity).

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes Entity details graph using less accuracy as entity itself  #18287
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

[bramkragten]

Why don't we pass the state?

[karwosts]

I thought about this, but looking at what getNumberFormatOptions does with the state, I'm not sure it made sense to use it.

The only thing it seems to check is if the current state is an integer. Should the current state of an entity affect how all its historical states are rendered?

[bramkragten]

Probably not, unless we assume the state was always an integer, which I dont think we can do.
More the step that might be useful.

[karwosts]

I guess you could combine the current step attribute, and the historical state value, merge them into a HassEntity, and pass that to the function.