Improve Lumetri curves with scale, point information and point selection in program window

In short, make the curves adjustment like the adjustment in Lightroom Classic.

The scopes window gives us information about the image, but that information is not easily translated over to the curves adjustment in Lumetri. At the bare minimum it’d be really useful to have a scale on the X-axis of the curves adjustment, but superimposing the histogram on the curves window would be even better. Additionally, it’d be very useful to add a point selection tool to the curves adjustment so that selecting a highlight or shadow point in the program window is super simple.