SF: Remove layer stack lookup for screencap

GPU virtual displays now have IDs, so the (ambiguous) fallback is no
longer necessary.

Remove PhysicalDisplayId constructor from uint64_t to enforce error
checking at compile time when upcasting or deserializing.

Bug: 162612135
Bug: 182939859
Test: screencap -d <id>
Test: DisplayId_test
Change-Id: I68fa0835cbc915975c7fa40c7d544d9491db9fa2
diff --git a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
index a3e8108..359e555 100644
--- a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
@@ -118,7 +118,7 @@
 
 sp<DisplayDevice> DisplayTransactionTest::injectDefaultInternalDisplay(
         std::function<void(FakeDisplayDeviceInjector&)> injectExtra) {
-    constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID(777);
+    constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId::fromPort(255u);
     constexpr int DEFAULT_DISPLAY_WIDTH = 1080;
     constexpr int DEFAULT_DISPLAY_HEIGHT = 1920;
     constexpr HWDisplayId DEFAULT_DISPLAY_HWC_DISPLAY_ID = 0;