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/SchedulerTest.cpp b/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
index 38e503f..7a6ae5b 100644
--- a/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
+++ b/services/surfaceflinger/tests/unittests/SchedulerTest.cpp
@@ -34,7 +34,7 @@
 namespace android {
 namespace {
 
-constexpr PhysicalDisplayId PHYSICAL_DISPLAY_ID(999);
+constexpr PhysicalDisplayId PHYSICAL_DISPLAY_ID = PhysicalDisplayId::fromPort(255u);
 
 class SchedulerTest : public testing::Test {
 protected: