[Search] Update AllApps header protection

- Disables header protection on AOSP
- Fades in/out search box pill instead of sudden movements
- Work tabs protection shows and hides based on scroll position

Bug: 194106968 [APK attached]
Test: Manual
Change-Id: I5532847ddba3d4555003b0934b8fc846dc5a5cc7

src/com/android/launcher3/ExtendedEditText.java

@@ -99,8 +99,18 @@ public class ExtendedEditText extends EditText {
         }
     }
 
-    // inherited class can override to change the appearance of the edit text.
-    public void show() {}
+    /**
+     * Sets whether EditText background should be visible
+     * @param maxAlpha defines the maximum alpha the background should animates to
+     */
+    public void setBackgroundVisibility(boolean visible, float maxAlpha) {}
+
+    /**
+     * Returns whether a visible background is set on EditText
+     */
+    public boolean getBackgroundVisibility() {
+        return getBackground() != null;
+    }
 
     public void showKeyboard() {
         mShowImeAfterFirstLayout = !showSoftInput();