Don't force public variables to use Hungarian notation (#8774)

People generally have expressed a dislike for the Hungarian notation
used in member variables, especially in examples/templates, and our
styleguide shouldn't be forced on downstream consumers, so this removes
all Hungarian notation from the examples/templates.

There are _some_ benefits to Hungarian for private member variables
(like knowing what's a member vs. local in a PR review) so we'll keep
private member variables the same for now, but public variables should
no longer use Hungarian notation, since it looks much worse. A new PMD
XPath rule has been added to accomplish this goal. Some other
non-compliant variables were fixed for the new rule.

wpilibj/src/main/java/org/wpilib/hardware/accelerometer/ADXL345_I2C.java

@@ -57,7 +57,6 @@ public class ADXL345_I2C implements NTSendable, AutoCloseable {
   }
 
   /** Container type for accelerations from all axes. */
-  @SuppressWarnings("MemberName")
   public static class AllAxes {
     /** Acceleration along the X axis in g-forces. */
     public double x;

wpilibj/src/main/java/org/wpilib/hardware/expansionhub/ExpansionHub.java

@@ -13,7 +13,7 @@ import org.wpilib.system.Timer;
 /** This class controls a REV ExpansionHub plugged in over USB to Systemcore. */
 public class ExpansionHub implements AutoCloseable {
   private static class DataStore implements AutoCloseable {
-    public final int m_usbId;
+    private final int m_usbId;
     private int m_refCount;
     private int m_reservedMotorMask;
     private int m_reservedServoMask;

wpilibj/src/main/java/org/wpilib/hardware/pneumatic/PneumaticHub.java

@@ -17,13 +17,13 @@ import org.wpilib.system.SensorUtil;
 /** Module class for controlling a REV Robotics Pneumatic Hub. */
 public class PneumaticHub implements PneumaticsBase {
   private static class DataStore implements AutoCloseable {
-    public final int m_module;
-    public final int m_handle;
+    private final int m_module;
+    private final int m_handle;
     private final int m_busId;
     private int m_refCount;
     private int m_reservedMask;
     private boolean m_compressorReserved;
-    public final int[] m_oneShotDurMs = new int[PortsJNI.getNumREVPHChannels()];
+    private final int[] m_oneShotDurMs = new int[PortsJNI.getNumREVPHChannels()];
     private final Object m_reserveLock = new Object();
 
     DataStore(int busId, int module) {

wpilibj/src/main/java/org/wpilib/hardware/pneumatic/PneumaticsControlModule.java

@@ -14,8 +14,8 @@ import org.wpilib.system.SensorUtil;
 /** Module class for controlling a Cross The Road Electronics Pneumatics Control Module. */
 public class PneumaticsControlModule implements PneumaticsBase {
   private static class DataStore implements AutoCloseable {
-    public final int m_module;
-    public final int m_handle;
+    private final int m_module;
+    private final int m_handle;
     private final int m_busId;
     private int m_refCount;
     private int m_reservedMask;