Function stellar_sql::sql::symbol::check_multi_keywords_front

pub fn check_multi_keywords_front(s: &str) -> Option<Vec<u32>>

Check if the word is the first word of any multi-word keywords, and then return how many words of all possible keywords. ex: alter could be alter table and alter column, so return Some(vec![2]) is could be is null and is not null, so return Some(vec![2, 3])