Relax input in functions that convert between colorspaces (bug #45456) * scripts/image/hsv2rgb.m, scripts/image/ntsc2rgb.m, scripts/image/rgb2hsv.m, scripts/image/rgb2ntsc.m: remove all input check and leave it up to new private functions handled by all. This adds support for ND images, drops check for values in the [0 1] range, allows integer images, and allows sparse matrices. Also adjust tests and add extra ones. * scripts/image/private/colorspace_conversion_input_check.m, scripts/image/private/colorspace_conversion_revert.m: all of this functions handle input check in the same way. In the same way, they need to prepare the output in the same way based on what preparation was done during input check (transforming image into colormap). So we create two new private functions to avoid repeated code. All code was adapted from hsv2rgb.