feat(evals): in `llm_classify`, use function calling to constrain LLM outputs when available; `llm_classify` now returns a dataframe (#1651)

* implement FunctionCallingClassifier with unit tests

* refactor response into openai response

* check input model type

* clean test case

* rename classifiers to evaluators

* fix types and styles

* rename

* fix unit tests

* remove evaluate method

* stylistic improvement

* add docstrings

* clean docstring

* update docstring

* update docstrings

* reduce PR scope by removing customizability of functions

* fix typo

* add toggle for disabling function calling

* add support indicator on model for function calling

* fix typo

* differentiate older azure api versions

* fix type check

* add code comments

* clean up

* fix type check

* remove with_explanation

* fix wording

* return dataframe instead of list

* update usage in README

* improve comments

* update notebooks

* add tests for column position

* clean up

* fix comment

* bump version

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Co-authored-by: Roger Yang <roger.yang@arize.com>