[build] Enable spotbugs (#3601)

Benign spotbugs warnings were suppressed, and all others were fixed. Bug
descriptions are documented here:
https://spotbugs.readthedocs.io/en/stable/bugDescriptions.html

Co-authored-by: Austin Shalit <austinshalit@gmail.com>

wpilibjIntegrationTests/src/main/java/edu/wpi/first/wpilibj/can/CANStatusTest.java

@@ -12,7 +12,7 @@ public class CANStatusTest {
   @Test
   public void canStatusGetDoesntThrow() {
     CANStatus status = new CANStatus();
-    CANJNI.GetCANStatus(status);
+    CANJNI.getCANStatus(status);
     // Nothing we can assert, so just make sure it didn't throw.
   }
 }