Benchmark methods that calculate boundaries.

[Kentzo]

There are a bunch of places where rects are needlessly re-calculated over most likely constant data.

E.g. intrinsicContentSize can just cache results of the rectForLabel call.

One of the approaches would be to have cache inside methods that calculate boundaries.
But first each method needs to be benchmarked, as maintaining cache is a burden.

[Kentzo]

@JanX2 Do you think you'd like to take a look at this?