Migrate stats page to db

[mashehu]

switched half of the code stats cards and the leader board (which for some reason loaded the stats.json increasing the load even further) a second time to be sourced from the database.

Load times are still rough...

[mashehu]

@nf-core-bot fix linting

[maxulysse]

@ewels @mashehu I think we can get rid of that

[ewels]

Leaving this as for now the new site will still load the old stats page. So this may still be relevant for a bit. Maybe.