Split the event describing a color space object

The following discussion from !6 (merged) should be addressed:

• @pq started a discussion: (+2 comments)

  I wonder if we should split this event into three, just like the create requests?

  It is not possible to send a not-fd in Wayland when an fd argument is required.

  If a client creates a color space from not an ICC file, the compositor does not need to manufacture an ICC file for the client to fetch, so a client can't use the compositor as an ICC file generator.

  For some HDR color spaces an ICC file is not even possible, which applies to both client created color spaces and output color spaces.

  A compositor should probably prefer to send all events it can, with the exception of not being required to manufacture an ICC file when it cannot or does not have one already. That way, a client gets also the well-known names when applicable. A client might even get the parametrized form in case it doesn't understand the well-known chromaticity name and ICC file doesn't apply.

As in the discussion that followed, if it's possible for a compositor to always manufacture a correct ICCv4 file, then the protocol can require it to be sent always, and have the other information sent only if applicable.