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.
Adds overloads for Transform2d() constructor to accept x, y, and heading and for Transform3d() to accept x, y, z and rotation as a shorthand for the normal constructors.
Comparison operators which compared against every class member variable
now use C++20's default comparison operators.
Also remove operator!= that in C++20 is now auto-generated from operator==.
