Paint Select: add Sample Merged option
Operating System: All
Description of the feature
Paint Select should have a "Sample Merged" option like Fuzzy Select and Select by Color tools. When the option is disabled, Paint Select would behave like it does now, working only with the active layer. When the option is enabled, Paint Select would base selection on all visible layers.
Use cases
Same reason, why other tools have this option. If the image is formed by combining multiple layers, it is possible that no single layer has the image that would lead to the desired selection shape.