[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>

cscore/src/test/java/edu/wpi/first/cscore/UsbCameraTest.java

@@ -21,7 +21,7 @@ import org.junit.jupiter.api.condition.OS;
 class UsbCameraTest {
   @Nested
   @EnabledOnOs(OS.LINUX)
-  class ConnectVerbose {
+  static class ConnectVerbose {
     @Test
     void setConnectVerboseEnabledTest() {
       try (UsbCamera camera = new UsbCamera("Nonexistant Camera", getNonexistentCameraDev())) {