Disable frivolous PMD warnings and enable PMD in ntcore (#3419)

Some valid warnings like throwing NullPointerException or using a for
loop instead of System.arraycopy() were fixed.

Abstract classes marked with PMD.AbstractClassWithoutAbstractMethod were
made concrete because they already had protected constructors.

Fixes #1697.

wpimath/src/test/java/edu/wpi/first/wpilibj/UtilityClassTest.java

@@ -19,6 +19,12 @@ import org.junit.jupiter.api.DynamicTest;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestFactory;
 
+// Declaring this class abstract prevents UtilityClassTest from running on itself and throwing the
+// following exception:
+//
+// org.junit.jupiter.api.extension.ParameterResolutionException: No ParameterResolver registered
+// for parameter [java.lang.Class<T> arg0] in constructor [protected
+// edu.wpi.first.wpilibj.UtilityClassTest(java.lang.Class<T>)].
 @SuppressWarnings("PMD.AbstractClassWithoutAbstractMethod")
 public abstract class UtilityClassTest<T> {
   private final Class<T> m_clazz;