API only (proposal): set CMS and desired output color encoding in decoder (#1366)
API only (proposal): set CMS and desired output color encoding in decoder (#1366)

* API only (proposal): set CMS and desired output color encoding in decoder

* remove JxlDecoderSetColorProfile

* default call to JxlDecoderSetCms and allow convert to greyscale ICC

* JxlDecoderSetOutputColorProfile

* explain how to use JxlDecoderSetOutputColorProfile

* refer to JxlDecoderSetOutputColorProfile

* typos

* editing...

* move around so that 'this' is correct

* allow convert to grayscale also from RGB

* simplify JxlDecoderSetCms

* fix errors

* Apply suggestions from code review

Co-authored-by: Jon Sneyers <44f878afe53efc66b76772bd845eb65944ed8232@cloudinary.com>

* review comments

* further review comments

* drop restriction for conversion

Co-authored-by: Moritz Firsching <c8f1a6aabac1f1b3e5245c40ceca966f954711d2@google.com>
libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl,libjxl/libjxl