Isolate a trace via legend should not hide traces with no legend entry

[alexcjohnson]

If you have a plot with some traces shown in the legend and some not (either because they were explicitly or implicitly omitted from the legend), double clicking one of the legend entries to isolate it seems like it shouldn't hide the traces that aren't in the legend at all.

legendgroup complicates this a bit - seems like if a trace can be toggled from the legend, it should disappear when isolating another trace; otherwise it should remain visible.

https://codepen.io/alexcjohnson/pen/MWWMVbr?editors=1010 - double-clicking one of the scatter legend entries hides the heatmap, but it should not.

From: https://community.plot.ly/t/preserving-ui-state-like-zoom-in-dcc-graph-with-uirevision/15793/64