Small cleanups to writing entity state

[bdraco]

Noticed while looking at the profiles from #89408

Proposed change

• Make friendly_name a bound method since it has no closure variables
• Remove duplicate local variables for self.registry_entry
• Avoid two dict lookups when DATA_CUSTOMIZE is in hass.data
• Reduce one possible access of self.name in broken out _friendly_name
• Save a few attribute lookups of self.entity_id

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 #
• This PR is related to issue:
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Checklist

• The code change is tested and works locally.
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