[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

wpilibjExamples/src/test/java/edu/wpi/first/wpilibj/examples/potentiometerpid/PotentiometerPIDTest.java

@@ -55,6 +55,7 @@ class PotentiometerPIDTest {
             0.0,
             Robot.kFullHeightMeters,
             true,
+            0,
             null);
     m_analogSim = new AnalogInputSim(Robot.kPotChannel);
     m_motorSim = new PWMSim(Robot.kMotorChannel);