[wpiutil, ntcore] Add structured data support (#5391)

This adds support for two serialization formats for complex data types:

- Protobuf for complex objects with variable length internals that need forward and backward wire compatibility (lower speed, more flexible)
- Raw struct (ByteBuffer-style) for fixed-length objects (higher speed, less flexible)

Deserialization can be done either by creating a new object (for immutable objects) or overwriting the contents of an existing object (for mutable objects).

Implementing classes should provide inner classes that implement the Protobuf or Struct interface (in Java) or specialize the wpi::Protobuf or wpi::Struct struct (in C++). It is possible for classes to implement both. If the class itself does not implement serialization, it's possible for third parties/users to provide an implementation instead.

Uses the Google protobuf implementation for C++ and the QuickBuffers alternative protobuf implementation for Java.

wpimath/src/main/native/cpp/geometry/Rotation3d.cpp

@@ -13,6 +13,7 @@
 #include <wpi/json.h>
 
 #include "frc/fmt/Eigen.h"
+#include "geometry3d.pb.h"
 #include "units/math.h"
 #include "wpimath/MathShared.h"
 
@@ -261,3 +262,21 @@ void frc::to_json(wpi::json& json, const Rotation3d& rotation) {
 void frc::from_json(const wpi::json& json, Rotation3d& rotation) {
   rotation = Rotation3d{json.at("quaternion").get<Quaternion>()};
 }
+
+google::protobuf::Message* wpi::Protobuf<frc::Rotation3d>::New(
+    google::protobuf::Arena* arena) {
+  return google::protobuf::Arena::CreateMessage<wpi::proto::ProtobufRotation3d>(
+      arena);
+}
+
+frc::Rotation3d wpi::Protobuf<frc::Rotation3d>::Unpack(
+    const google::protobuf::Message& msg) {
+  auto m = static_cast<const wpi::proto::ProtobufRotation3d*>(&msg);
+  return Rotation3d{wpi::UnpackProtobuf<frc::Quaternion>(m->q())};
+}
+
+void wpi::Protobuf<frc::Rotation3d>::Pack(google::protobuf::Message* msg,
+                                          const frc::Rotation3d& value) {
+  auto m = static_cast<wpi::proto::ProtobufRotation3d*>(msg);
+  wpi::PackProtobuf(m->mutable_q(), value.GetQuaternion());
+}