Client unable to configure model parameters

[TaoChenOSU]

The client currently cannot configure parameters (TopP, temperature...) for the completion model used in the summarization handler and the Ask API: https://github.com/microsoft/semantic-memory/blob/main/dotnet/CoreLib/Search/SearchClient.cs#L312

Would be useful to be able to configure those parameters.

[dluc]

Since #673 the summarization handler allows to customize the prompt. However, the handler is designed for precision, e.g. using temperature = 0 on purpose.
It's possible to inject custom handlers and use a completely different approach if needed.