Finish making clang-tidy (mostly) work (again) and run -fix (#2312)

This does some more work to the run_clang_tidy.py wrapper script, and runs an example pass.

"again" because it's really the proto fuzzer changes that broke it, it had been working before.

"mostly" because there's still an issue within the proto fuzzer that it can't find "port/protobuf.h", i.e. https://github.com/google/libprotobuf-mutator/tree/master/port, but I'm still hesitant to add an include path there.

explorer/ast/pattern.h

@@ -275,10 +275,11 @@ class GenericBinding : public Pattern {
 
   // Return the original generic binding.
   auto original() const -> Nonnull<const GenericBinding*> {
-    if (original_.has_value())
+    if (original_.has_value()) {
       return *original_;
-    else
+    } else {
       return this;
+    }
   }
   // Set the original generic binding.
   void set_original(Nonnull<const GenericBinding*> orig) { original_ = orig; }