Set up analytics tracking for hot reload times in Flutter

[biggs0125]

In order to ensure DDC's hot reload workflow is (and stays) performant we should set up analytics tracking in Flutter.

[kevmoo]

@biggs0125 – from our analytics, I think this is "fixed", right?

[srujzs]

I think we have what we need and can feasibly get. We can reopen this if we think our current analytics is insufficient.