Rename system-api wm flags to SYSTEM_...

Also add a special API to set them. Internally they are still just
regular private flags

Test: Built
Bug: 116798569
Change-Id: I687b751fa18c7fbcc9bf95aa44d94d8a5614a88f
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBarWindowController.java b/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBarWindowController.java
index 57c7e28..0d37b55 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBarWindowController.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBarWindowController.java
@@ -173,9 +173,9 @@
         }
 
         if (state.dozing) {
-            mLpChanged.privateFlags |= LayoutParams.PRIVATE_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS;
+            mLpChanged.privateFlags |= LayoutParams.SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS;
         } else {
-            mLpChanged.privateFlags &= ~LayoutParams.PRIVATE_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS;
+            mLpChanged.privateFlags &= ~LayoutParams.SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS;
         }
     }