Add "Fixed Static" and "Fixed Error" color roles

[etyarews]

Is your feature request related to a problem? Please describe. Each static/extended/custom color generate 4 colors: color, on-main color, container color, and on-container color. This is not enough and doesn't offer any option for the brightness to stay the same

Describe the solution you'd like While still lacking in exports (per issue #281), Accent Colors were recently updated to include fixed variants, color-fixed, color-fixed-dim, on-color-fixed, on-color-fixed-variant. The same system could be added for static and error color roles

Additional context Recently, we've run into a problem where we want to give users the option to choose between a small selection of color pairing (background and foreground pairs), the issue is that users don't expect the color chosen to change brightness level based on light and dark mode, and we want to uss static colors as a means to offer a limited palette that still meshes well with the rest of the UI, and fixed static colors would help a lot with that