[wpilib] Document simulation APIs (#3079)

- Remove sim checkstyle suppression
- Add [[nodiscard]] to C++ register callback functions
- Add a couple of missing sim functions

Co-authored-by: Peter Johnson <johnson.peter@gmail.com>
Co-authored-by: Starlight220 <yotamshlomi@gmail.com>

hal/src/main/java/edu/wpi/first/hal/SimDevice.java

@@ -4,7 +4,17 @@
 
 package edu.wpi.first.hal;
 
-/** A wrapper around a simulator device handle. */
+/**
+ * A wrapper around a simulator device handle.
+ *
+ * <p>Teams: if you are using this class, you are likely confusing it for {@link
+ * edu.wpi.first.wpilibj.simulation.SimDeviceSim}.
+ *
+ * <p>Vendors: This class should be used from inside the device class to define the
+ * properties/fields of the device. Use {@link #create} to get a SimDevice object, then use {@link
+ * #createDouble(String, Direction, double)} or similar to define the device's fields. See {@link
+ * edu.wpi.first.wpilibj.ADXRS450_Gyro} for an example implementation.
+ */
 public class SimDevice implements AutoCloseable {
   public enum Direction {
     kInput(SimDeviceJNI.kInput),