use field init shorthand EVERYWHERE

Like #43008 (f668999), but _much more aggressive_.

src/libstd/path.rs

@@ -2049,7 +2049,7 @@ impl Path {
         let prefix = parse_prefix(self.as_os_str());
         Components {
             path: self.as_u8_slice(),
-            prefix: prefix,
+            prefix,
             has_physical_root: has_physical_root(self.as_u8_slice(), prefix),
             front: State::Prefix,
             back: State::Body,