Implement extract_cellset_async

[MariusWirtz]

Implement extract_cellset_async and expose function through execute_mdx and execute_view leverages extract_cellset_axes_raw_async and extract_cellset_cells_raw_asyncfunctions

Still lacking test cases but performance improvements are already measurable.

[MariusWirtz]

@vmitsenko
Is this what you had in mind when you introduced extract_cellset_axes_raw_async and extract_cellset_cells_raw_async in August last year?

[vmitsenko]

@MariusWirtz
Yes, exactly. There have also been ideas about incorporating it directly in "extract_cellset_raw" with an additional parameter to avoid creating a lot of additional "..._async", but there are doubts whether this would be a coherent approach.

[MariusWirtz]

I see. The alternative to be introducing another _async function would be to add max_workers to the execute_mdx function.

I will stick to currently established patterns. I think long term we can deprecate the _async functions

[MariusWirtz]

@MariusWirtz Yes, exactly. There have also been ideas about incorporating it directly in "extract_cellset_raw" with an additional parameter to avoid creating a lot of additional "..._async", but there are doubts whether this would be a coherent approach.

Actually, adding the max_workers and async_axis arguments to the execute_mdx and execute_view simplifies the development and maintenance of the test cases.
So, I already included it in the PR.

[vmitsenko]

Small changes added, all tests passed successfully.