Hey team 👋

I found a pretty nasty libvips behavior appeared because of #3623 (more specifically: 0d665ba). This PR adds stripping ICC profiles when converting from/to scRGB. While this seems correct at first glance, this also makes vips behave unpredictably.

For example, you import ICC with vips_icc_import and then convert the image to sRGB. Since the conversion from XYZ/LAB to sRGB goes through vips_sRGB2scRGB_build, it removes the ICC profile from the image. The same happens if you apply vips_sharpen and convert the image back to sRGB.