Use defaulted comparison operators in C++ (#4723)

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==.

wpimath/src/main/native/include/frc/geometry/Twist2d.h

@@ -46,14 +46,6 @@ struct WPILIB_DLLEXPORT Twist2d {
            units::math::abs(dtheta - other.dtheta) < 1E-9_rad;
   }
 
-  /**
-   * Checks inequality between this Twist2d and another object.
-   *
-   * @param other The other object.
-   * @return Whether the two objects are not equal.
-   */
-  bool operator!=(const Twist2d& other) const { return !operator==(other); }
-
   /**
    * Scale this by a given factor.
    *