HeatmapGraphic, supports dims larger than 8192

[kushalkolar]

Performance is very fast, tested with a 10,000 x 108,000 array, uses 4GB of VRAM. All features work, data slicing and setting, cmap, vmin vmax.

heatmap.mp4

note:

• currently all Tiles that make up the heatmap are updated when the data are modified, this affects performance but we are assuming that people don't need heatmaps to update at 100Hz 😂
• will need to think of event handling, perhaps we can make a new feature events for HeatmapGraphic, and perhaps ImageGraphic too, called "row-clicked" or "col-clicked", which parse the low level pygfx "click" event and emit row or column index with respect to the data displayed in the graphic. We probably want to have multi row or multi column selection too