Enable Ecto Psql Extras for live dashboard query stats

[grossvogel]

This should give us lots more useful query info in our live dashboard.

https://github.com/pawurb/ecto_psql_extras
https://github.com/phoenixframework/phoenix_live_dashboard/blob/master/guides/ecto_stats.md

NOTE: we'll probably have to update LiveView and use the latest LiveDashboard for this to work

[revelry-stalebot]

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