[wpilib] Simulation: Add ctor parameter to set starting state of mechanism sims (#5288)

- Add a constructor parameter to configure the initial angle of the arm
- Also reorganizes cascading constructors for Java

wpilibc/src/main/native/include/frc/simulation/ElevatorSim.h

@@ -32,12 +32,13 @@ class ElevatorSim : public LinearSystemSim<2, 1, 1> {
    * @param minHeight          The minimum allowed height of the elevator.
    * @param maxHeight          The maximum allowed height of the elevator.
    * @param simulateGravity    Whether gravity should be simulated or not.
+   * @param startingHeight     The starting height of the elevator.
    * @param measurementStdDevs The standard deviation of the measurements.
    */
   ElevatorSim(const LinearSystem<2, 1, 1>& plant, const DCMotor& gearbox,
               double gearing, units::meter_t drumRadius,
               units::meter_t minHeight, units::meter_t maxHeight,
-              bool simulateGravity,
+              bool simulateGravity, units::meter_t startingHeight,
               const std::array<double, 1>& measurementStdDevs = {0.0});
 
   /**
@@ -53,12 +54,13 @@ class ElevatorSim : public LinearSystemSim<2, 1, 1> {
    * @param minHeight          The minimum allowed height of the elevator.
    * @param maxHeight          The maximum allowed height of the elevator.
    * @param simulateGravity    Whether gravity should be simulated or not.
+   * @param startingHeight     The starting height of the elevator.
    * @param measurementStdDevs The standard deviation of the measurements.
    */
   ElevatorSim(const DCMotor& gearbox, double gearing,
               units::kilogram_t carriageMass, units::meter_t drumRadius,
               units::meter_t minHeight, units::meter_t maxHeight,
-              bool simulateGravity,
+              bool simulateGravity, units::meter_t startingHeight,
               const std::array<double, 1>& measurementStdDevs = {0.0});
 
   /**