[wpimath] Deprecate RamseteController (#6494)

LTVUnicycleController is a drop-in replacement with better tuning knobs.

The RamseteCommand examples were removed instead of retrofitted with
LTVUnicycleController because we're planning on removing the command
controller classes anyway, so it would be wasted effort. The
SimpleDifferentialDriveSimulation example shows direct
LTVUnicycleController usage.

wpimath/src/test/native/cpp/controller/RamseteControllerTest.cpp

@@ -3,6 +3,7 @@
 // the WPILib BSD license file in the root directory of this project.
 
 #include <gtest/gtest.h>
+#include <wpi/deprecated.h>
 
 #include "frc/MathUtil.h"
 #include "frc/controller/RamseteController.h"
@@ -16,6 +17,8 @@ static constexpr units::meter_t kTolerance{1 / 12.0};
 static constexpr units::radian_t kAngularTolerance{2.0 * std::numbers::pi /
                                                    180.0};
 
+WPI_IGNORE_DEPRECATED
+
 TEST(RamseteControllerTest, ReachesReference) {
   frc::RamseteController controller{2.0 * 1_rad * 1_rad / (1_m * 1_m),
                                     0.7 / 1_rad};
@@ -43,3 +46,5 @@ TEST(RamseteControllerTest, ReachesReference) {
                                       robotPose.Rotation().Radians()),
                     0_rad, kAngularTolerance);
 }
+
+WPI_UNIGNORE_DEPRECATED