Add missing WSMAN class fetch functions for complete diagnostics coverage

[ShradhaGupta31]

The rpc WSMAN diagnostics command (rpc wsman get --class ) relies on the wsmanClassFetchers map to fetch device state per class. Currently, not all classes have a dedicated fetch function, several classes use the generic rawWSMANClassFetcher fallback instead of a dedicated typed fetch function. This fallback sends raw SOAP XML and returns an unstructured XML string, making the output harder to validate, test, and consume programmatically.

The expectation is that every registered class has a dedicated typed fetch function that calls the library's structured API and returns a typed Go response.

list of classes can be found here - device-management-toolkit/rpc-go#1005