fix googleai recursive tool conversion: add missing fields in recursive tool conversion

[sami-sweng]

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Closes #1234, improves #1326 by adding missing parse of nullable and enum. Also better support what is thrown at it, for instance declaration parsed from yaml which are map[any] by default.

[layou233]

Can we have jsonschema support for Google AI? It just looks a subset of the genai.Schema, and it would help multiplatform development. 🥰