Update `AsyncScalarUDFImpl` API to match `ScalarUDFImpl `API

[alamb]

Is your feature request related to a problem or challenge?

• Introduce Async User Defined Functions  #14837 introduces AsyncScalarUDFImpl to run async functions 🥳 🦜 🚀

However, the API is slightly different than the ScalarUDFImpl which has evolved (specifically I am thinking about return_type instead of return_field, etc)

Here is the async definition
https://github.com/apache/datafusion/blob/cdaaef79e68665fe7f70f0864b0ff4e4a02eab9d/datafusion/expr/src/async_udf.rs#L87-L86

Describe the solution you'd like

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Additional context

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