[wpilib] Deprecate getInstance() in favor of static functions (#3440)

Co-authored-by: Noam Zaks <imnoamzaks@gmail.com>

wpilibjIntegrationTests/src/main/java/edu/wpi/first/wpilibj/CounterTest.java

@@ -66,7 +66,7 @@ public class CounterTest extends AbstractComsSetup {
     // port}.
     // These data are hard-coded into the class, but they could be
     // generated or loaded in any way you like.
-    return TestBench.getInstance().getDIOCrossConnectCollection();
+    return TestBench.getDIOCrossConnectCollection();
   }
 
   @BeforeClass