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.

wpiutil/src/test/java/org/wpilib/util/cleanup/CleanupPoolTest.java

@@ -13,6 +13,7 @@ import java.util.List;
 import org.junit.jupiter.api.Test;
 
 class CleanupPoolTest {
+  @SuppressWarnings("PMD.PublicFieldNamingConvention")
   static class AutoCloseableObject implements AutoCloseable {
     public boolean m_closed;
 

wpiutil/src/test/java/org/wpilib/util/cleanup/ReflectionCleanupTest.java

@@ -10,6 +10,7 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
 import org.junit.jupiter.api.Test;
 
 class ReflectionCleanupTest {
+  @SuppressWarnings("PMD.PublicFieldNamingConvention")
   static class CleanupClass implements AutoCloseable {
     public boolean m_closed;
 
@@ -19,7 +20,7 @@ class ReflectionCleanupTest {
     }
   }
 
-  @SuppressWarnings("PMD.TestClassWithoutTestCases")
+  @SuppressWarnings({"PMD.TestClassWithoutTestCases", "PMD.PublicFieldNamingConvention"})
   static class CleanupTest implements ReflectionCleanup {
     public CleanupClass m_class1 = new CleanupClass();
     public CleanupClass m_class2 = new CleanupClass();
@@ -32,6 +33,7 @@ class ReflectionCleanupTest {
     }
   }
 
+  @SuppressWarnings("PMD.PublicFieldNamingConvention")
   static class CleanupTest2 extends CleanupTest {
     @SkipCleanup public CleanupClass m_class3 = new CleanupClass();
     public CleanupClass m_class4 = new CleanupClass();

wpiutil/src/test/java/org/wpilib/util/struct/DynamicStructTest.java

@@ -20,7 +20,6 @@ import org.junit.jupiter.params.provider.MethodSource;
 
 @SuppressWarnings("AvoidEscapedUnicodeCharacters")
 class DynamicStructTest {
-  @SuppressWarnings("MemberName")
   private StructDescriptorDatabase db;
 
   @BeforeEach