Revert "ui: Refactor stable ID generation for GPU virtual displays"

This reverts commit 78c90af2224b43467d854e356492527db0f8eb70.

Reason for revert: Causes assert for certain GPU virtual display Ids in VirtualDisplaySurface.cpp (https://paste.googleplex.com/6474098414977024)

Change-Id: I743312bbab4fd9903e069c3ed4710f9d7901be8d
diff --git a/services/surfaceflinger/DisplayDevice.h b/services/surfaceflinger/DisplayDevice.h
index ef3e77d..c2d09c9 100644
--- a/services/surfaceflinger/DisplayDevice.h
+++ b/services/surfaceflinger/DisplayDevice.h
@@ -89,7 +89,7 @@
         return mCompositionDisplay;
     }
 
-    bool isVirtual() const { return getId().isVirtual(); }
+    bool isVirtual() const { return VirtualDisplayId::tryCast(getId()).has_value(); }
     bool isPrimary() const { return mIsPrimary; }
 
     // isSecure indicates whether this display can be trusted to display