The flamegraph tooltip could show aggregate timings too

Interesting idea from this old bugzilla bug https://bugzilla.mozilla.org/show_bug.cgi?id=1148186:

> I should be able to just hover over a frame in the flame graph and it should show that frame's
>
> * function name and location
> * self time (for this specific frame in the flame graph)
> * total time (for this specific frame in the flame graph)
> * aggregate self time (for all instances of this frame in the flame graph)
> * aggregate total time (for all instances of this frame in the flame graph)
> * aggregate percent of samples where this frame was the leaf

I think we miss the 3 last ones, but we could have them quite easily.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-537)