Simplify contains check that opts-in to contains_literal fast-path (

#3736)

* improve check that can automatically opt-in to the "contains_literal" fast-path

* simplify fast-path check, unwinding regex-syntax dependency

polars/polars-ops/src/chunked_array/strings/namespace.rs

@@ -102,10 +102,7 @@ pub trait Utf8NameSpaceImpl: AsUtf8 {
 
     /// Check if strings contain a regex pattern; select literal fast-path if no special chars
     fn contains(&self, pat: &str) -> Result<BooleanChunked> {
-        if pat
-            .chars()
-            .all(|c| c.is_alphanumeric() || c.is_whitespace() || (c == '_'))
-        {
+        if pat.chars().all(|c| !c.is_ascii_punctuation()) {
             self.contains_literal(pat)
         } else {
             let ca = self.as_utf8();

polars/tests/it/lazy/expressions/arity.rs

@@ -87,7 +87,7 @@ fn includes_null_predicate_3038() -> Result<()> {
                 move |s| {
                     s.utf8()?
                         .to_lowercase()
-                        .contains("non-existent")
+                        .contains_literal("non-existent")
                         .map(Into::into)
                 },
                 GetOutput::from_type(DataType::Boolean),