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.

wpiutil/src/test/java/edu/wpi/first/wpiutil/CircularBufferTest.java

@@ -105,7 +105,6 @@ class CircularBufferTest {
   }
 
   @Test
-  @SuppressWarnings("PMD.ExcessiveMethodLength")
   void resizeTest() {
     CircularBuffer queue = new CircularBuffer(5);