Fix LauncherProvider newScreenId issue

Remove maxScreenId from LauncherProvider and whenever we need
a new screenId, query the database to calculate a new screenId.
Also converted and refactored AddWorkspaceItemsTaskTest
and added some extra test cases.

Test: manual & AddWorkspaceItemsTaskTest.kt
Bug: 199160559
Change-Id: I185f6823fed171d778af0130497f5ffaf89c0a70

src/com/android/launcher3/model/ModelWriter.java

@@ -292,7 +292,7 @@ public class ModelWriter {
         FileLog.d(TAG, "removing items from db " + items.stream().map(
                 (item) -> item.getTargetComponent() == null ? ""
                         : item.getTargetComponent().getPackageName()).collect(
-                Collectors.joining(",")), new Exception());
+                Collectors.joining(",")));
         notifyDelete(items);
         enqueueDeleteRunnable(() -> {
             for (ItemInfo item : items) {