SF: Cleanup creating / destroying virtual display APIs

Follow-up CL for cleanup requested by SF owner in http://ag/27202517.

Misc:
- Fix type conversion warnings for print format.
- Return status destroying virtual display in SF and add appropriate
checks in UT.
- Use static constexpr / const for compile-time effciciency.

Bug: 339525838
Bug: 137375833
Bug: 194863377
Test: atest libsurfaceflinger_unittest
Test: atest SurfaceFlinger_test
Flag: EXEMPT refactor
Change-Id: I7859720989c9244b26f8764c3323a8495064c888
diff --git a/services/surfaceflinger/tests/MultiDisplayLayerBounds_test.cpp b/services/surfaceflinger/tests/MultiDisplayLayerBounds_test.cpp
index 7fce7e9..56cf13d 100644
--- a/services/surfaceflinger/tests/MultiDisplayLayerBounds_test.cpp
+++ b/services/surfaceflinger/tests/MultiDisplayLayerBounds_test.cpp
@@ -53,14 +53,15 @@
     }
 
     virtual void TearDown() {
-        SurfaceComposerClient::destroyDisplay(mVirtualDisplay);
+        EXPECT_EQ(NO_ERROR, SurfaceComposerClient::destroyVirtualDisplay(mVirtualDisplay));
         LayerTransactionTest::TearDown();
         mColorLayer = 0;
     }
 
     void createDisplay(const ui::Size& layerStackSize, ui::LayerStack layerStack) {
+        static const std::string kDisplayName("VirtualDisplay");
         mVirtualDisplay =
-                SurfaceComposerClient::createDisplay(String8("VirtualDisplay"), false /*secure*/);
+                SurfaceComposerClient::createVirtualDisplay(kDisplayName, false /*isSecure*/);
         asTransaction([&](Transaction& t) {
             t.setDisplaySurface(mVirtualDisplay, mProducer);
             t.setDisplayLayerStack(mVirtualDisplay, layerStack);