Currently, when color-picking from the viewport, the code will read the final
displayed pixel color and then somewhat attempt to undo the display transform.
However, this has several limitations - for example, precision is limited to 8
bit, and it does not account for e.g. View Transform or exposure/gamma.
Since we have the pre-display-transform color in a GPU texture anyways, this
code therefore adds a View3D-specific eyedropper handler (similar to e.g.
the image space) that reads from the viewport texture.
Pull Request: https://projects.blender.org/blender/blender/pulls/123408
fd2bc9d011