AlarmDecoder config flow fixes

[ajschmidt8]

Proposed change

This PR addresses some comments from @MartinHjelmare in #37998 after it was merged.

Specifically, the changes include:

• Using async_add_executor_job for controller.close()
• Refactoring service registrations
• Renaming devices to entities
• Removing some extraneous return True statements
• Using some common values in strings.json
• Adding config entries before options flow in unit tests
• Refactoring the baud variable usage to remove some code duplication from tests

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

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# Example configuration.yaml

Additional information

• This PR fixes or closes issue: fixes #
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[MartinHjelmare]

Please also update the config flow to use the executor when opening the controller connection.

[ajschmidt8]

Please also update the config flow to use the executor when opening the controller connection.

@MartinHjelmare done in d02254f & d0adca7.

I tested these locally and they worked, but please review the second commit in particular to make sure it looks okay

[MartinHjelmare]

Great!