Only aggregate weekly data for pings

Created by: dadlerj

Fixes https://github.com/sourcegraph/sourcegraph/issues/10612

Now is your chance @efritz @attfarhan to change the "period" that we aggregate by! I'm making it so that we ONLY aggregate by week now, but if you need something else, or think something else would be more helpful, feel free to suggest changes. We can do multiple periods if needed of course.

@tsenart this doesn't "solve" the issues we're seeing but it certainly helps with https://github.com/sourcegraph/sourcegraph/issues/10598