Marginal 2D labels

[ndmlny-qs]

Feature Description

Add point statistic labels to the marginal 2D tool, just like the marginal 1D tool has. See image below as reference.

[ndmlny-qs]

@horizon-blue I think I will work on this after #1819 has been merged. That way we can include both the labels as well as allowing the user to choose which point statistic they want to display; the mean or median of the distributions.