This commit adds gimp_color_selector_set_format() which is meant to give
awareness of the target color format for which we are selecting colors.
Right now, I am only using this information on the Scales selection
method, which means that now colors you read and select are in the
target space. Even better, the out-of-gamut shown happens in the with
LCH scales is for the target space too. As tested, it already makes
quite a difference for an image in sRGB vs. say adobeRGB.
Note that right now, I only use the format information as a space, but
in fact, I made the API to be about a format because the actual format
can be used wisely too. First we may want to do different thing
depending on the color model itself (which the space may give away or
not, especially when using default spaces or when we'll have images
using models with no space in the future, such as CIE Lab). But also
whether the image is following the space TRC or is linear (or
perceptual) would change how we represent the data. If we were to show
non-linear values in the Colors dockable but when painting, the color
picker shows linear values for instance, it might be puzzling to people.
e104196cb7