Extract function name in get_schema_from_signature

[eitanturok]

Currently, get_schema_from_signature creates a json where "title": "Arguments". This PR changes this so that the "title" will instead be mapped to the function's name.

Here is an example. I have this code snippet:

from outlines.fsm.json_schema import get_schema_from_signature

def test_add(a: int, b: int | None = None):
    if b is None:
        return a
    return a + b

schema = get_schema_from_signature(test_add)
print(schema)

Before this PR, this outputted

{'properties': {'a': {'title': 'A', 'type': 'integer'}, 'b': {'anyOf': [{'type': 'integer'}, {'type': 'null'}], 'title': 'B'}}, 'required': ['a', 'b'], 'title': 'Arguments', 'type': 'object'}

and after this PR, this outputted

{'properties': {'a': {'title': 'A', 'type': 'integer'}, 'b': {'anyOf': [{'type': 'integer'}, {'type': 'null'}], 'title': 'B'}}, 'required': ['a', 'b'], 'title': 'test_add', 'type': 'object'}

(Scroll to see the 'title' key.)

[eitanturok]

Initial discussion occurred in #863.

[leloykun]

ah, I also raised a (now duplicate) PR 😅

#875

I'll close mine