regex: migrate grep-regex to regex-automata

We just do a "basic" dumb migration. We don't try to improve anything
here.

Cargo.lock

@@ -200,6 +200,7 @@ dependencies = [
  "grep-matcher",
  "log",
  "regex",
+ "regex-automata 0.3.0",
  "regex-syntax",
  "thread_local",
 ]