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ARROW-10317: [Python] Document compute function options

Add docstrings for parameters of the various function options classes.
Automatically ingest those parameter docstrings into the generated compute function docstrings
(this uses vendored code from `numpydoc`).

Example with the `min_max` parameter docs:

* before:
```
array : Array-like
    Argument to compute function
skip_nulls : optional
    Parameter for ScalarAggregateOptions constructor. Either `options`
    or `skip_nulls` can be passed, but not both at the same time.
min_count : optional
    Parameter for ScalarAggregateOptions constructor. Either `options`
    or `min_count` can be passed, but not both at the same time.
options : pyarrow.compute.ScalarAggregateOptions, optional
    Parameters altering compute function semantics.
memory_pool : pyarrow.MemoryPool, optional
    If not passed, will allocate memory from the default memory pool.
```

* after:
```
array : Array-like
    Argument to compute function.
skip_nulls : bool, default True
    Whether to skip (ignore) nulls in the input.
    If False, any null in the input forces the output to null.
min_count : int, default 1
    Minimum number of non-null values in the input.  If the number
    of non-null values is below `min_count`, the output is null.
options : pyarrow.compute.ScalarAggregateOptions, optional
    Alternative way of passing options.
memory_pool : pyarrow.MemoryPool, optional
    If not passed, will allocate memory from the default memory pool.
```

Closes #12076 from pitrou/ARROW-10317-py-doc-function-options

Authored-by: Antoine Pitrou <antoine@python.org>
Signed-off-by: Antoine Pitrou <antoine@python.org>