use given rtol/atol in SessionComparator listwidget

[gdementen]

Currently the given rtol/atol is used in the widget on the right but has no effect on the red coloring of the array names on the left which is confusing and annoying.

If we fix that, we will want to also update the list when we change the tolerance, which will be slow.

While it is super handy for "smallish" sessions (you immediately see which arrays have differences), computing that list color systematically may not be the best idea. Unsure how to keep the handy side but avoid a sluggish interface when comparing largish sessions. @alixdamman Do you have an idea to reconcile the two?

Also, if we fix this problem, we might want to move the tolerance & "show differences only" widgets somewhere else to make it more obvious they have an effect for all arrays comparisons, not just the current one.