Fix spurious test failures (wpilibsuite#338)

* Fix spurious test failures with AllWidgetSanityTest

Were caused by values being set on the FX Thread instead of the test thread
Still no idea why it was only for the tests for PIDCommand and Graph widgets

* Fix spurious failure with NumberFieldTest

Was caused by clearing the field when not on the FX thread

api/src/test/java/edu/wpi/first/shuffleboard/api/components/NumberFieldTest.java

@@ -23,7 +23,7 @@ public void start(Stage stage) throws Exception {
 
   @Test
   public void numberPropertyIsUpdatedTest() {
-    numberField.clear();
+    interact(numberField::clear);
     clickOn(".text-field").write("123.456");
 
     assertEquals(123.456, numberField.numberProperty().getValue().doubleValue());
@@ -32,7 +32,7 @@ public void numberPropertyIsUpdatedTest() {
   @ParameterizedTest
   @ValueSource(strings = {"0.0", "1.0", "12.56", "-0", "-1", "-10", "+0", "+55.99", "-54.21"})
   public void validNumberTest(String number) {
-    numberField.clear();
+    interact(numberField::clear);
     clickOn(".text-field").write(number);
 
     assertEquals(Double.parseDouble(number), numberField.getNumber().doubleValue());
@@ -45,7 +45,7 @@ public void validNumberTest(String number) {
                  "0.0, 0.......0",
                  "0.0, 0.0."})
   public void invalidNumberTest(String expectedResult, String test) {
-    numberField.clear();
+    interact(numberField::clear);
     clickOn(".text-field").write(test);
 
     assertEquals(expectedResult, numberField.getText());

plugins/base/src/test/java/edu/wpi/first/shuffleboard/plugin/base/widget/AllWidgetSanityTest.java

@@ -3,6 +3,8 @@
 import edu.wpi.first.shuffleboard.api.data.DataType;
 import edu.wpi.first.shuffleboard.api.data.DataTypes;
 import edu.wpi.first.shuffleboard.api.sources.DummySource;
+import edu.wpi.first.shuffleboard.api.util.AsyncUtils;
+import edu.wpi.first.shuffleboard.api.util.FxUtils;
 import edu.wpi.first.shuffleboard.api.util.TypeUtils;
 import edu.wpi.first.shuffleboard.api.widget.Widget;
 import edu.wpi.first.shuffleboard.api.widget.WidgetType;
@@ -28,13 +30,15 @@ public class AllWidgetSanityTest extends ApplicationTest {
 
   @BeforeAll
   public static void setup() {
+    AsyncUtils.setAsyncRunner(Runnable::run);
     DataTypes.setDefault(new DataTypes());
     plugin.getDataTypes().forEach(DataTypes.getDefault()::register);
   }
 
   @AfterAll
   public static void tearDown() {
     DataTypes.setDefault(new DataTypes());
+    AsyncUtils.setAsyncRunner(FxUtils::runOnFxThread);
   }
 
   @ParameterizedTest