Follow new ArviZ development

[aloctavodia]

The new ArviZ is getting in shape and many functions in ArviZ-legacy are already usable see https://arviz-plots.readthedocs.io/en/latest/ we should evaluate what functionality we are going to use from that project and also inform its development given the requirements of arviz-dashboard

[OriolAbril]

Moreover, there is still a lot of room to influence arviz-plots so it can be a better fit for dashboards. For example: arviz-devs/arviz-plots#68