Small profiling additions and changed back to qFuzzyCompare

Now it's possible to see the time spent in synchronizing and emitting contact signals.

This showed quite some time is spent for synchronizing when there are many active bodies, even when they are not really changing visually. The time could be reduced somewhat by reverting back to `qFuzzyCompare`, which avoids tiny changes in position and rotation triggering a change on the Qt Quick side.

The emitSignals time will be mostly due to the `contactChanged` signal. I suggest we remove this again once that signal is gone since I don't think it's that useful afterwards.