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.

datalog/src/main/java/org/wpilib/datalog/DataLogRecord.java

@@ -124,7 +124,6 @@ public class DataLogRecord {
    * Data contained in a start control record as created by DataLog.start() when writing the log.
    * This can be read by calling getStartData().
    */
-  @SuppressWarnings("MemberName")
   public static class StartRecordData {
     StartRecordData(int entry, String name, String type, String metadata) {
       this.entry = entry;
@@ -169,7 +168,6 @@ public class DataLogRecord {
    * Data contained in a set metadata control record as created by DataLog.setMetadata(). This can
    * be read by calling getSetMetadataData().
    */
-  @SuppressWarnings("MemberName")
   public static class MetadataRecordData {
     MetadataRecordData(int entry, String metadata) {
       this.entry = entry;

datalog/src/test/java/org/wpilib/datalog/DataLogTest.java

@@ -119,7 +119,6 @@ class DataLogTest {
     }
   }
 
-  @SuppressWarnings("MemberName")
   private static int cloneCalls;
 
   static class CloneableThing implements StructSerializable, Cloneable {
@@ -201,10 +200,8 @@ class DataLogTest {
     public static final ThingStruct struct = new ThingStruct();
   }
 
-  @SuppressWarnings("MemberName")
   private ByteArrayOutputStream data;
 
-  @SuppressWarnings("MemberName")
   private DataLog log;
 
   @BeforeEach