add device kwarg to astype API

[steff456]

This PR,

• Adds device kwarg to astype API in the DRAFT version

It fixes #647 (comment)

[kgryte]

LGTM.

[leofang]

LGTM too. One possible nit: IIRC we discussed about raising exceptions for casting to unsupported dtypes by a certain device. Do we want to address it in this PR, or another?

I'd like to have @oleksandr-pavlyk to take a look if possible.

[kgryte]

@leofang Ah, you're right. We do need to address the condition where the requested device does not support the desired dtype. Although, this applies more generally to all creation functions supporting the dtype kwarg. In which case, maybe we do want to address in a follow-up PR which covers all affected APIs?

[leofang]

Yup sounds good

[ogrisel]

Thanks for the PR, LGTM as well.

[kgryte]

LGTM. Thanks, @steff456!

[kgryte]

As this PR has three approvals, will go ahead and merge.

We'll submit a follow-up PR to add guidance concerning what should happen when a device does not support an array data type when using astype and various creation functions.