[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),

hal/src/main/java/edu/wpi/first/hal/simulation/RoboRioDataJNI.java

@@ -7,13 +7,17 @@ package edu.wpi.first.hal.simulation;
 import edu.wpi.first.hal.JNIWrapper;
 
 public class RoboRioDataJNI extends JNIWrapper {
+  @SuppressWarnings("AbbreviationAsWordInName")
   public static native int registerFPGAButtonCallback(
       NotifyCallback callback, boolean initialNotify);
 
+  @SuppressWarnings("AbbreviationAsWordInName")
   public static native void cancelFPGAButtonCallback(int uid);
 
+  @SuppressWarnings("AbbreviationAsWordInName")
   public static native boolean getFPGAButton();
 
+  @SuppressWarnings("AbbreviationAsWordInName")
   public static native void setFPGAButton(boolean fPGAButton);
 
   public static native int registerVInVoltageCallback(

hal/src/main/java/edu/wpi/first/hal/simulation/SimDeviceDataJNI.java

@@ -29,6 +29,7 @@ public class SimDeviceDataJNI extends JNIWrapper {
   public static native int getSimValueDeviceHandle(int handle);
 
   public static class SimDeviceInfo {
+    @SuppressWarnings("JavadocMethod")
     public SimDeviceInfo(String name, int handle) {
       this.name = name;
       this.handle = handle;
@@ -62,6 +63,7 @@ public class SimDeviceDataJNI extends JNIWrapper {
   public static native int getSimValueHandle(int device, String name);
 
   public static class SimValueInfo {
+    @SuppressWarnings("JavadocMethod")
     public SimValueInfo(
         String name, int handle, int direction, int type, long value1, double value2) {
       this.name = name;