Adds header protection on tablet all apps panel.

Removes background and manually draws it while drawing scrim. Then
draws header protection on top as needed.

Currently this only applies to all apps from Launcher, as Taskbar
doesn't seem to use the same scrim flow. So taskbar adds the same
static background that was previously used.

Demo videos: https://drive.google.com/drive/folders/11PyFsrLV6-QhU_E-zD3s5bfzZK2nOU87?resourcekey=0-E41uw5TP9xuqTifLAs71yw&usp=sharing

Test: Manually on phone and tablet with dark/light mode, floating
search bar on/off, work profile present/absent, taskbar/home entry
Bug: 240670050

Change-Id: I81dcc956d9dbbc7552c8a227a49741bcf71eed71

src/com/android/launcher3/allapps/ActivityAllAppsContainerView.java

@@ -282,6 +282,10 @@ public class ActivityAllAppsContainerView<T extends Context & AppLauncher
     @Override
     public int getHeaderBottom() {
         if (FeatureFlags.ENABLE_FLOATING_SEARCH_BAR.get()) {
+            if (mActivityContext.getDeviceProfile().isTablet) {
+                return super.getHeaderBottom() + mHeader.getClipTop()
+                        + mBottomSheetBackground.getTop();
+            }
             return super.getHeaderBottom() + mHeader.getClipTop();
         }
         return super.getHeaderBottom() + mSearchContainer.getBottom();