Retrieves appliance preconfigurations with flexible filtering options. Returns different response structures based on query parameters:

• No parameters: Returns all preconfigurations with full details including base64-encoded configData
• preconfigId: Returns a single preconfiguration by ID
• filter=names: Returns only preconfiguration names (lightweight)
• filter=metadata: Returns metadata without the configData field

Note: filter and preconfigId parameters are mutually exclusive.