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/CompositionTest.cpp b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
index 3042450..e42cf47 100644
--- a/services/surfaceflinger/tests/unittests/CompositionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/CompositionTest.cpp
@@ -77,7 +77,7 @@
 constexpr hal::HWLayerId HWC_LAYER = 5000;
 constexpr Transform DEFAULT_TRANSFORM = static_cast<Transform>(0);
 
-constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID(42);
+constexpr PhysicalDisplayId DEFAULT_DISPLAY_ID = PhysicalDisplayId::fromPort(42u);
 constexpr int DEFAULT_DISPLAY_WIDTH = 1920;
 constexpr int DEFAULT_DISPLAY_HEIGHT = 1024;