feat: transformed theme-specific global vars to theme-agnostic (#DS-2755)

[NikGurev]

Theming unified

Global semantic colors have been placed under theme selectors and prefixes for variables removed - so they do not depend on the theme. For example:

Before

// css-tokens.css
--kbq-light-theme-default: color;
--kbq-dark-theme-default: otherColor;

After

// css-tokens-light.css
.kbq-light {
   --kbq-theme-default: color;
   ... other theme specific colors
}

// css-tokens-dark.css
.kbq-light {
   --kbq-theme-default: otherColor;
   ... other theme specific colors
}