Obihai to have common unique_ids with DHCP or without

[ejpenney]

Proposed change

DHCP Info and PyObihai.get_device_mac have different casing, so depending on the setup path, users can sometimes see DHCP discovery for an already configured device. Everything now uses format_mac(), for consitency.

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 #92625
• This PR is related to issue: N/A
• Link to documentation pull request: N/A

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[home-assistant]

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

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Comments addressed

[epenet]

LGTM 👍
Please adjust the PR description now that the standardisation rule has changed.