Violin plot: avoid cropping long tick labels

[vladsavelyev]

It's the xaxis.automargin parameter that usually controls if Plotly should account for the tick length when calculating the plot height, so they are not cropped. Unfortunately, it does it by taking space from the allocated layout.height instead of adding more height. This is usually okay for other plot types, where we don't mind them squishing a bit. However, for the violins, we build them by stacking multiple subplots, and when we have a lot of thin violins, adding space to one of them to fit the labels will squash all other violins too much, making them unreadable. Also, Plotly will only expand space for the bottom violin, ignoring the rest. So we need to find a workaround to add space for long tick labels, but keep the actual violins constant height.