Not clear if scaled min and max equal normal caps if scaling not supported

It is not immediately clear if `VkSurfacePresentScalingCapabilitiesEXT::minScaledImageExtent` equals `VkSurfaceCapabilitiesKHR::minImageExtent` if `supportedPresentScaling == 0`. Or whether the value can be garbage in that case.

Review the descriptions of VkSurfacePresentScalingCapabilitiesEXT and VkSurfaceCapabilitiesKHR, focusing on minScaledImageExtent, minImageExtent, and supportedPresentScaling. Clarify in the specification whether unsupported scaling makes the scaled extents equivalent to the normal caps or leaves them undefined, and ensure the resulting wording answers the issue directly.

Written by the indexing model from the issue text.