Data Table: the $data-table-zebra-color token is a hard-coded un-themed hex value

[jendowns]

Detailed description

The $data-table-zebra-color is a theme token that applies to all odd-numbered rows in a zebra DataTable, but the token is actually a hard-coded hex value and therefore it breaks for all dark themes (i.e., appears as #FCFCFC and is unreadable).

See: https://github.com/IBM/carbon-components/blob/master/src/globals/scss/_theme-tokens.scss#L203

 $data-table-zebra-color: #fcfcfc !default !global;

Ideally this token should instead use a role-based token from @carbon/themes so that it can work for dark UI themes.