[css-color-5] Need new `<color>` production

[svgeesus]

CSS Color 4 defines the <color> type.

CSS Color 5 extends each of the color functions with Relative Color Syntax and also adds @color-profile and custom color spaces to color() and device-cmyk().

As pointed out here:

• [css-color-5] Nested relative colors #7963

this leads to an interpretation that RCS cannot be nested, because the definition of <color> predates RCS.

Thus, CSS Color 5, which is still a delta spec, needs an updated definition of <color> which includes all these.

[svgeesus]

c17a10d