Allow integrations to specify the "domain" of the entity that is rendered in previews

[iluvdata]

Breaking change

None seen in testing.

Proposed change

Allow integration developers to specific the "domain" and a preview entity created in data entry flows. Currently the frontend selects the entity rended based on the step_id of the flow. Also allow repairs_flows to utilized developed previews.

Screenshots

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

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue or discussion:
• Link to documentation pull request:
• Link to developer documentation pull request: Data entry flow previews developers.home-assistant#3081
• Link to backend pull request:

Checklist

• I understand the code I am submitting and can explain how it works.
• The code change is tested and works locally.
• There is no commented out code in this PR.
• I have followed the [perfect PR recommendations][perfect-pr]
• Any generated code has been carefully reviewed for correctness and compliance with project standards.

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

• Documentation added/updated for [www.home-assistant.io][docs-repository]

To help with the load of incoming pull requests:

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