.Net: KernelInvocationChatClient as a specialization of FunctionInvokingChatClient

[rogerbarreto]

Currently due to limitations in the current MEAI's FunctionInvoking types, including the FunctionInvokingChatClient, we needed to create a full reimplementation of it in our KernelInvocationChatClient, this issue is a Task to investigate what would need to change in the current FunctionInvokingChatClient to allow minimal changes from SK so we could just extend from FunctionInvokingChatClient and override where necessary.