Commands to engine (#3448)

* commands to engine

* Correction of error in parser

* Added detailed regex error to parse

* better regex error parsing

* clippy corrections

* parse example with test

* secondary error for regex

* removed clone in error parser

* Secondary error message

crates/nu-command/tests/commands/parse.rs

@@ -181,7 +181,7 @@ mod regex {
                 "#
             ));
 
-            assert!(actual.err.contains("invalid regex"));
+            assert!(actual.err.contains("unclosed group"));
         })
     }
 }