Function push_both_delimiters

fn push_both_delimiters<'s, 'v>(
    entered: &Stack<'v, EnteredDelimiter<'s, 'v>>,
    lhs_delim: &'s Syntax<'s>,
    rhs_delim: &'s Syntax<'s>,
    alloc: &'v Bump,
) -> Stack<'v, EnteredDelimiter<'s, 'v>>