test(node): add OSConfig Default traits

[andrewbattat]

NODE-1808

Adds GuestOSConfig, HostOSConfig, and SetupOSConfig Default trains to reduce test boilerplate. Unit tests now only must specify specific fields they care about.

[github-actions]

This pull request modifies the IC-OS configuration types library (rs/ic_os/config_types/src/lib.rs).

Please ensure you have followed the Configuration Update Protocol guidelines——particularly if adding a new enum or enum variants:

Enum Variant Forward Compatibility Guidelines: If adding a new enum or new variants to an enum, ensure older versions can handle unknown variants gracefully by using #[serde(other)] on a fallback variant. See examples: GuestVMType::Unknown and Ipv6Config::Unknown.

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For complete guidelines, see the documentation at the top of rs/ic_os/config_types/src/lib.rs.

CONFIG_TYPES_COMPATIBILITY_REMINDER_DEDUP

Only changes to test code