Retrieve the data for the dashboard from Matomo

[bfabio]

The website chart in the dashboard shows data fetched from Google Analytics, but now that it's gone it will lag behind

We need to implement this: https://github.com/teamdigitale/dpt-services-dashboard-scripts/issues/34

Adding the issue here as well because it's more likely to be looked for here.

[bfabio]

Ditto for forum.italia.it

[bfabio]

Depends on https://github.com/AgID/wai-portal/pull/1321