Refactor Folder to use ActivityContext and BaseDragLayer

These are the more generic versions of Launcher and DragLayer, so
that Folders can be used in other surfaces.

Test: Open and close Folders on home screen, ensure works properly
Bug: 171917176
Change-Id: I39b9aedbd8319ca61ea0e776bc95eab585e023d5
diff --git a/src/com/android/launcher3/BaseActivity.java b/src/com/android/launcher3/BaseActivity.java
index 8a03fac..062ab71 100644
--- a/src/com/android/launcher3/BaseActivity.java
+++ b/src/com/android/launcher3/BaseActivity.java
@@ -31,7 +31,6 @@
 import android.os.Bundle;
 import android.os.UserHandle;
 import android.util.Log;
-import android.view.ContextThemeWrapper;
 
 import androidx.annotation.IntDef;
 
@@ -333,7 +332,7 @@
     public static <T extends BaseActivity> T fromContext(Context context) {
         if (context instanceof BaseActivity) {
             return (T) context;
-        } else if (context instanceof ContextThemeWrapper) {
+        } else if (context instanceof ContextWrapper) {
             return fromContext(((ContextWrapper) context).getBaseContext());
         } else {
             throw new IllegalArgumentException("Cannot find BaseActivity in parent tree");