[UI/Core Split] Refactor GetSupportedPlatforms in Utilities

[benfleuty]

The GetSupportedPlatforms method in Utilities.cs determines the supported platforms based on configuration settings. This logic is related to server configuration and is a piece of core business logic, not a general UI or collection utility. While it doesn't directly interact with UI, its location in a broad Utilities class is not ideal in a well-structured core.

To improve code organization within the core, this method should be moved to a service or class directly related to server configuration or platform management.

Action:

1. Create a new core-level class related to server configuration or platform handling (e.g., ServerConfigurationService.cs or PlatformService.cs).
2. Move the GetSupportedPlatforms method to this new class.
3. Update any code that uses GetSupportedPlatforms to reference the new class.
4. Add or update tests for the platform determination logic.