Incorporate latest API changes in code examples

[thomasclaudiushuber]

With Windows App SDK 1.8-experimental1 some APIs have changed that are not in the docs yet:

• the PackageDeploymentStatus enum does not exist anymore. Instead, the AIFeatureReadyResultState enum is used.
• ExtendedError() is not a method anymore, but a property instead
• GenerateResponseAsync returns a LanguageModelResponseResult and no more a LanguageModelResponse object
• LanguageModelResponseResult does not have the response in a Response property, but in a Text property
• GenerateResponseWithProgressAsync does not exist anymore, it's now just GenerateResponseAsync
• Some examples contain a var result declaration inside an if-statement and a var result declaration outside of the if-statement, which causes the code to not compile due to CS0136 error (A local or parameter named 'result' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter). I call the variable for the response response instead of result to avoid this.

This PR fixes these things in the code examples to make them valid for Windows App SDK 1.8-experimental1.