Revert "WidgetModel: deprecate getChoices & move to iface"

This reverts commit 8794f7a.

This change broke scijava-ui-swing, because item.getChoices() can
return null. However, even when guarding against null, there is
another problem: the current implementation in DefaultWidgetModel
leans on the ObjectService, which is not accessible at the
WidgetModel interface level. So for now, let's just revert this
change. All seems to work fine without meddling here.

Author: ctrueden

src/main/java/org/scijava/widget/DefaultWidgetModel.java

@@ -218,6 +218,17 @@ public Number getStepSize() {
 		return NumberUtils.toNumber("1", item.getType());
 	}
 
+	@Override
+	public String[] getChoices() {
+		final List<?> choicesList = getItem().getChoices();
+		if (choicesList == null) return null;
+		final String[] choices = new String[choicesList.size()];
+		for (int i = 0; i < choices.length; i++) {
+			choices[i] = objectService.getName(choicesList.get(i));
+		}
+		return choices;
+	}
+
 	@Override
 	public String getText() {
 		final Object value = getValue();

src/main/java/org/scijava/widget/WidgetModel.java

@@ -134,13 +134,13 @@ public interface WidgetModel extends Contextual {
 	 */
 	Number getStepSize();
 
-	/** @deprecated Use {@code getItem().getChoices()} instead. */
-	@Deprecated
-	default String[] getChoices() {
-		return getItem().getChoices().stream() //
-			.map(choice -> choice.toString()) //
-			.toArray(String[]::new);
-	}
+	/**
+	 * Gets the multiple choice list for the module input.
+	 * 
+	 * @return The available choices, or an empty list if not multiple choice.
+	 * @see ChoiceWidget
+	 */
+	String[] getChoices();
 
 	/**
 	 * Gets the input's value rendered as a string.