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.

migrate_cpp/rewriter.cpp

@@ -16,18 +16,18 @@ auto OutputWriter::Write(clang::SourceLocation loc,
                          const OutputSegment& segment) const -> bool {
   return std::visit(
       [&](auto& content) {
-        using type = std::decay_t<decltype(content)>;
+        using Type = std::decay_t<decltype(content)>;
         auto [begin, end] = bounds;
 
-        if constexpr (std::is_same_v<type, std::string>) {
+        if constexpr (std::is_same_v<Type, std::string>) {
           auto begin_offset = source_manager.getDecomposedLoc(loc).second;
           // Append the string replacement if the node being replaced falls
           // within `bounds`.
           if (begin <= begin_offset && begin_offset < end) {
             output.append(content);
           }
-        } else if constexpr (std::is_same_v<type, clang::DynTypedNode> ||
-                             std::is_same_v<type, clang::TypeLoc>) {
+        } else if constexpr (std::is_same_v<Type, clang::DynTypedNode> ||
+                             std::is_same_v<Type, clang::TypeLoc>) {
           auto content_loc = content.getSourceRange().getBegin();
           auto begin_offset =
               source_manager.getDecomposedLoc(content_loc).second;
@@ -54,7 +54,7 @@ auto OutputWriter::Write(clang::SourceLocation loc,
             }
           }
         } else {
-          static_assert(std::is_void_v<type>,
+          static_assert(std::is_void_v<Type>,
                         "Failed to handle a case in the `std::variant`.");
         }
         return true;