Make taskbar focusable when folder is open to get IME input

- Remove ActivityContext#supportsIme(), as it's always true now
- Add OnFolderStateChangedListener, which we register when clicking on a taskbar folder icon to set the window focusable/not.
- Also remove Folder.STATE_NONE and instead default to STATE_CLOSED (renamed from STATE_SMALL).

TODO: make sure back button is visible above IME (followup CL)

Test: Open a folder from taskbar while in an app, no animation jump and can change folder name
Bug: 180051157
Change-Id: I7c7847657d462c16677d66b9ffa8b6fe5f164084

src/com/android/launcher3/util/UiThreadHelper.java

@@ -28,7 +28,6 @@ import android.os.Message;
 import android.view.View;
 import android.view.inputmethod.InputMethodManager;
 
-import com.android.launcher3.BaseActivity;
 import com.android.launcher3.views.ActivityContext;
 
 /**
@@ -56,7 +55,7 @@ public class UiThreadHelper {
                 STATS_LOGGER_KEY,
                 Message.obtain(
                         HANDLER.get(root.getContext()),
-                        () -> BaseActivity.fromContext(root.getContext())
+                        () -> ActivityContext.lookupContext(root.getContext())
                                 .getStatsLogManager()
                                 .logger()
                                 .log(LAUNCHER_ALLAPPS_KEYBOARD_CLOSED)