deps: initial migration steps to regex 1.9

This leaves the grep-regex crate in tatters. Pretty much the entire
thing needs to be re-worked. The upshot is that it should result in some
big simplifications. I hope.

The idea here is to drop down and actually use regex-automata 0.3
instead of the regex crate itself.

crates/core/args.rs

@@ -1464,7 +1464,7 @@ impl ArgMatches {
         // own, but if the patterns are joined in a set of alternations, then
         // you wind up with `foo|`, which is currently invalid in Rust's regex
         // engine.
-        "(?:z{0})*".to_string()
+        "(?:)".to_string()
     }
 
     /// Converts an OsStr pattern to a String pattern. The pattern is escaped