warn directive trivia are not compatible with fantomas #18636
Description
When adding "scoped nowarn" (#18049), I misinterpreted how trivia are meant to be used. While working on the necessary Fantomas adaptation, I found now I should follow the way trivia for conditional directives (#if) are handled. This means that the whole line (including indentation and possibly comment) has to be reported as trivia. Currently, the comment is reported separately. Having two trivia in a row, however, cannot easily be handled in Fantomas. And consistency with conditional directives makes sense anyway.