Use attribute docstrings for options

[jyu00]

What is the expected feature or enhancement?

Today most of the options dataclasses use the same Google style argument docstring as the rest of the modules. Unfortunately, the rendered API reference would list each field under both Parameters and Attributes, for example:

The one exception is SamplerExecutionOptions, which only has attribute docstring. The generated doc therefore only shows the fields under Attributes:

I think this is a much nicer format, as you get both the description and type in one place.

@Eric-Arellano please let us know if you have better ideas!

Acceptance criteria

• Use attribute docstring instead of argument docstring for options classes.

Also note that when I played with SamplerExecutionOptions, the text Default: True was not formatted correctly, so I don't know if there is special convention on specifying defaults.