.Net: Check `ChatResponseMessage.FunctionToolCalls` metadata compatability

[SergeyMenshykh]

Type of ChatResponseMessage.FunctionToolCalls metadata has changed from Enumerable<ChatCompletionsFunctionToolCall> to IEnumerable<ChatToolCall>.

Check if the types are compatible from a serialization point of view. In other words, is it possible to deserialize the old type to the new one?

See the parent issue #7053 for more details.