Load leaks in DisplayActivity as they're loaded

[jrodbx]

Thanks to #1081, I get a bunch of false alarms which I ignore. However, when I face a leak that I now care about and go to the DisplayActivity, I have to wait for all of them to load (I currently have 91), before appearing in the Activity list. An impatient user may think they have no leaks to review and exit the Activity prematurely.

A quick workaround might be to post a notification, but I'd prefer for each leak to appear in the list as soon as it's been loaded in a least-recent to most-recent order.

[pyricau]

Great idea!

• Seems fairly doable to load leaks one at a time, since we have one leak per file
• We can first list the total number of file (to get an accurate list size) and then replace template items with real items
• We should probably reverse the order as well to have latest at the top? Seems like that's what you want to see most of the time.

[pyricau]

Note: this should happen after #1202 (which changes the UX by adding groups)

[pyricau]

LeakCanary now stores the data as rows in a Sqlite db, which should be much faster. Also, we now display groups so there should be way less rows. The db is read from a background IO thread and the full list displayed. Changing this to a dynamic list that requeries as we scroll but in a background thread (picasso like) seems like much more work.

If this becomes an issue again, we could look into this, or optimizing the SQL query, or cleaning up old data.