Replace taskbar hotseat with real hotseat when folder is open

- Seamlessly show real hotseat and hide taskbar hotseat, while
  keeping rest of taskbar visible
- Update MultiValueAlpha to allow for taking max alpha instead
  of blending, and use that for Hotseat
- Fix folder open bounds on home screen when taskbar is present

Test: Open folder from taskbar on home, can drag out items
Bug: 182079330
Bug: 171917176
Change-Id: I7c1983e3219b1341cf233260f0ccac9051c4dc14
diff --git a/src/com/android/launcher3/DeviceProfile.java b/src/com/android/launcher3/DeviceProfile.java
index 2440854..fb7a99f 100644
--- a/src/com/android/launcher3/DeviceProfile.java
+++ b/src/com/android/launcher3/DeviceProfile.java
@@ -708,10 +708,11 @@
                     mInsets.top + availableHeightPx);
         } else {
             // Folders should only appear below the drop target bar and above the hotseat
+            int hotseatTop = isTaskbarPresent ? taskbarSize : hotseatBarSizePx;
             return new Rect(mInsets.left + edgeMarginPx,
                     mInsets.top + dropTargetBarSizePx + edgeMarginPx,
                     mInsets.left + availableWidthPx - edgeMarginPx,
-                    mInsets.top + availableHeightPx - hotseatBarSizePx
+                    mInsets.top + availableHeightPx - hotseatTop
                             - workspacePageIndicatorHeight - edgeMarginPx);
         }
     }