Add tool support to OllamaChatGenerator when streaming (or raise an error)

[sjrl]

Is your feature request related to a problem? Please describe.
I noticed in the OllamaChatGenerator that when streaming we ignore the tool_calls field of ollama.Message when collecting the chunks to eventually make the ChatMessage.

Describe the solution you'd like
We should either add support for it if possible or throw an error at init time and runtime if streaming + tools is requested like we do in the HuggingFaceAPIChatGenerator.

[anakin87]

Ollama now supports streaming + tool calls: https://ollama.com/blog/streaming-tool.
Introduced in 0.8.0.