Function find_matches_within_haystack

pub fn find_matches_within_haystack<'a>(
    haystack: &'a str,
    pattern: &str,
    case_insensitive: bool,
    outer: bool,
) -> (Vec<Match<'a>>, Option<Regex>)

This function is the basis for both pattern_matches_vec() and pattern_matches_outer() and will be used with string-patterns-extras to replicate look-ahead and look-behind behaviour It returns a flattened vector of Match objects The outer options limits the matches to the whole matched sequence and excludes inner groups