Large pings with lots of charts slow down DPV

[rosahbruno]

Example: https://debug-ping-preview.firebaseapp.com/pings/chutten-glean/a76c309e-3149-44ab-8c47-4f76ffd5a03d

Lets look into optimizing how we render here. Few things we can try

1. memoize the charts, make sure they aren't rerendering too often on first load
2. only show the first N number of charts per metric type, then have a "show more" button if someone needs to see the rest.. 4 or 6 would probably be a good number to start with