[Stats Refresh] Investigate Stats parsing performance

[jklausa]

During testing, I've found some operations can take painfully long time to finish in the new Stats architecture — e.g. viewing a list of referres for a whole year takes ages.

Fetching summary also takes very long time, as mentioned by @ScoutHarris.

We need to profile this and fix the issues.

[jklausa]

At first glance it seems it's not due to parsing at all, but rather UIKit is doing something really bizarre...

Note the runtime in minutes!!!

Like it's trying to display millions of row at the same time?

[jklausa]

(to be fair, the runtime is much less dramatic when not being instrumented... but still.)

[jklausa]

So I think I know what is going on here.

@ScoutHarris I think there's some work required on how the details screen are displayed.

Right now it's just a single UITableViewCell (TopTotalsCell) that has a UIStackView that contains all the items in it. This works fine for a small amount of objects, but breaks down rather... badly for lists with HUGE count of items in it. Displaying "Clicks" for the past year for en.blog causes the cell to grow to almost 40000pt in height.

Turns out, iOS doesn't handle trying to render bitmaps this large well :D

I think we need to make this use actual UITableViewCells, instead of the "fake" ones in the UIStackView.

[ScoutHarris]

Created #11657 for the summary. I'll address the StackViews with a series of PRs.

[ScoutHarris]

All details views have been fixed on referenced PRs.