MAINT: Use the base ``nipreps/miniconda`` image

[oesteban]

This should ease the issues we are having with some dependencies (esp. hdf5) as well as make the building process more standardized across nipreps. In the long run it should also help minimize build time, as we converge towards multi-stage builds where source images have been minimized.

[oesteban]

@celprov we need to do something like this on the mriqc front

[celprov]

@oesteban, I was assigned for review , but what does it entail ?