output: Check the EDID for the supported sink Colorimetry
Just like the HDR Metadata property the Colorspace property values only indicate that the display driver supports signaling certain colorimetry. It does not indidcate that the sink actually supports processing the colorimetry. For this we have to look up the colorimetry support in the EDID.
The default colorimetry is always supported. If we want bt.2020 we might get either the RGB or YCC variant so we have to check support for both.