Make download part of ehrdata

[eroell]

Description of feature

The _dataloader module is currently private. Should we make it be part of the public API? It is useful for downloading datasets, and could also be so for other developers.

The least reduces redundancy for us, without us using private modules across repos

https://github.com/theislab/ehrapy/blob/0a74f705650e71485de44d5054cd7145e27c4d62/ehrapy/data/_dataloader.py#L17

[Zethson]

I could see it become a part of ehrdata and ehrapy depend on ehrdata. WDYT?

[eroell]

Sounds good to me :+1:

[eroell]

Completed with https://github.com/theislab/ehrdata/pull/136.

The current use of ehrapy's download function in its datasets will be removed as per in ehrapy's dataset deprecationwarnings