main: Create a no-op color manager for the remoting plug-in

The color manager gets checks and has a fallback loading after the backends get loaded. The plug-ins though, like remoting or pipewire would enable the outputs much sooner, so export the no-op color manager object to be able to create one before enabling the output and finding that there's color manager at all.

Signed-off-by: Marius Vlad marius.vlad@collabora.com