feat: Add tools/functions variables to Jinja2ChatFormatter, add function response formatting for all simple chat formats (#1273)

* Add tools/functions variables to Jinja2ChatFormatter

Also fixed missing tools/tool_choices parameters in chat_formatter_to_chat_completion_handler().

* Set grammar when doing explicit function calling

* Add function / tool response for all chat formats

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Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>