feat(header): implement fmt::Display for several headers

Specifically, `CacheControl`, `Expect`, `Origin`, `Pragma`, `Prefer`,
`PreferenceApplied`, `ReferrerPolicy`, `StrictTransportSecurity`.

src/header/common/expect.rs

@@ -55,6 +55,12 @@ impl Header for Expect {
     }
 
     fn fmt_header(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+impl fmt::Display for Expect {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.write_str("100-continue")
     }
 }