NAS-133930 / 25.10 / Clean-up device info plugin

[yocalebo]

This cleans up the device info module.

1. remove methods that were only used in unit tests? The actual method wasn't called anywhere...
2. remove methods that aren't called anywhere else
3. move the tty serial information to ups module since that's the only caller
4. remove unused imports

[bugclerk]

Jira URL: https://ixsystems.atlassian.net/browse/NAS-133930

[bugclerk]

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